Mental prayer is a must for every single Christian. I would dare to say that our crisis in the Christian faith today - having so many non-practicing Christians - is due to a crisis in prayer; it is a lack of an authentic, humble, sincere and daily, intimate encounter with God.
Fr. Jacques Philippe in his book Time for Prayer talks about two traps that people fall into with regards to their thinking about prayer:
Thinking that prayer is optional, and
Thinking that I don’t need to pray. “I can just go to Mass” or “I can just receive the sacraments.”
Finally, if we do pray daily (and we ought to lest we violate the first Commandment by not putting God first, daily), one should ask, "But what kind of prayer is it?"
In order to truly deepen our union with God and be Christians in the world, not worldly Christians, we need to enter into deeper prayer. Were we not told?...
Do not conform yourselves to this age but be transformed by the renewal of your mind, that you may discern what is the will of God, what is good and pleasing and perfect. [Romans 12:2]
Prayer is what causes this transformation. To put prayer simply, our Catechism references St. Therese of Lisieux who says, "With me prayer is an uplifting of the heart; a glance towards heaven; a cry of gratitude and love, uttered equally in sorrow and in joy.” St. Teresa of Avila says, "Prayer is only a friendly intercourse in which the soul converses along with Him by whom she knows that she is loved."
Catholics are often comfortable with vocal prayer but mental prayer seems to be unidentified territory. Here is a link that simply explains mental prayer and gives you a method to get you started. Yet it's important to remember, however, that the method is only a means to get you meditating on Christian truths, the life of Christ, etc... so that you can elevate your heart and converse with God. From here, we can give God plenty of working room that, in time, can lead us into a much deeper intimacy with God (which she explains in her crowning work The Interior Castle).
8 reasons you should be practicing mental prayer, every day.
I will be drawing from the spiritual classic called The Ways of Mental Prayer and pulling from it these eight effects mental prayer will have on the Christian.
1. It enlightens our understanding.
On the part of the understanding, there is ignorance of the supernatural life. To listen attentively to the word of God or to read it carefully is already a beginning of meditation. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
Through this, we can learn more about the truths of our Faith and begin to see things from God's perspective and His Wisdom, rather than limiting ourselves to this world and the so-called wisdom of it, which our Lord refers to as "foolishness."
For the wisdom of this world is foolishness in the eyes of God. [1 Corinthians 3:19]
2. It puts to flight our spiritual sloth and lukewarmness.
Hence it comes to pass that even amongst good souls, who live by grace, there are so many weak, so many slumbering. When we forget God and the things of God, we have still the eye of faith, but it is half closed by spiritual drowsiness. The end to be aimed at, the virtues to be practiced, the rocks to be avoided, - everything is clouded over, nothing distinctly outlined. Hope is without desire, charity without fervor; the other virtues lose their activity; torpor (spiritual lethargy or laziness) reigns everywhere. We sleep and we dream; and while our eyes are closed towards God, our imagination is taken up with a thousand foolish fancies as in a dream, our memory is filled with a thousand frivolous recollections, our intellect exhausts itself in useless thoughts in the preoccupations of our work and office...
...What can arouse us from this wretched sluggishness, if not the practice of mental prayer! Little by little, mental prayer well made will render our faith more lively, will strengthen our convictions, will penetrate us deeply with the things of God, will keep the supernatural ways present to our mind. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
Often, even those striving to live a Christian life struggle with this paralyzing spiritual sloth which dries up devotion and fervor. We do what we must as Christians but lack zeal for souls and proclaiming the truth in season and out of season. We are slow to turn toward spiritual things and prefer to turn to the things of the world. Rather than spend extra time in prayer, we turn on the television or browse the internet and social media. We ponder unimportant things that have no relevance to our salvation, the Lord or our vocation (take, for example, the overspeculation of sports analysis that our culture is obsessed with and consumes minds; another example is the entertainment industry...). Fr. Lehodey (who echoes the saints) suggests that this is due to a lack of mental prayer, and mental prayer made well. This preoccupation drains our interior life of true depth and purpose.
3. It gives us true self-knowledge.
Self-love blinds us; humiliated by our many miseries and faults and discouraged by the difficulty of remedying them, we prefer to shut our eyes. Hence, no longer seeing the faults we have to correct, and the enemies we have to combat, we either cease to fight, or merely beat the air...We hardly know the virtues we want, the weak points we should strengthen, and spiritual life will drift away aimlessly at the mercy of every passing impulse. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
Fr. Lehodey gives us the remedy of a daily examination of conscience, especially the self-examination which is made during mental prayer.
For, after showing us the ideal we should follow, mental prayer invites us to consider the reforms we have to make...it is especially the school of humility...Mental prayer enables us to put our finger upon the multitude of our faults, defects, and imperfections...and it becomes the grave of pride. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
Often, we think we know ourselves and we slap a label on the things we perceive we struggle with. And even while we may be correct, the practice of mental prayer can help shine a light on perhaps a root cause of that particular struggle - something we would have never thought of on our own were it not for God who revealed it to us. Or, while we are working to remedy a particular vice, the Lord, through the regular practice of mental prayer, may direct us towards some other fault of ours that actually has a greater grip on us. Mental prayer gives us true self-knowledge.
4. It detaches us from sin.
Concupiscence is the inclination we have toward sin and to do evil. Since the fall of Adam and Eve, we've inherited a disordered desire to do things we ought not to do. (For example, one may have the desire to lust upon someone, even though they know they should not as it objectifies the person. That disordered desire to lust is called concupiscence).
Detachment from sin means that there is no one sin which the soul is unwilling to renounce. Having an attachment to sin puts one in bondage. For example, even though one might realize that lying is wrong, they are still willing to do it when it comes to situations in which they could be reprimanded or receive consequences. Thus, in order to avoid a penalty - say - from a boss at work, they tell a "little" lie to cover themselves. A detachment from sin would mean that, after the person realizes what they're doing is wrong or is a manipulation, they are willing to give it up. If someone is attached to this sin of lying - no matter how small - they would not be willing to bear the consequences truthfully and would sadly continue in their sinful way.
An attachment involves a refusal to amend a situation, and a person should be able to tell if he has such an attachment. Sometimes, deep down, we really don’t want to let go of certain sins, be it gossiping or overeating or loafing on the job. This differs from the case of normal human weakness or where a person falls into the same sin many times before overcoming it. To souls such as these the Church is ready to open her treasury of aid. [Father Edward McIlmail, Q&A: Total Detachment from Sin]
What happens through prayer, however, is the Lord begins to transform and change our hearts according to His. So whereas telling a little lie was once attractive to gain some benefit, God has transformed the heart into no longer desiring to do that, even though the temptation itself may still present.
5. It detaches us from temporal things.
...such as riches, honor, bodily comfort, of all which things it is so easy to make an ill use. It shows us the vanity of all that cannot satisfy a heart hungering after God, the inconstancy and frailty of all that passes away, the anxieties and dangers these false good brings with them, and their utter worthlessness is comparison with what lasts forever. "How empty appears the earth to him who contemplates heaven!" How its joys and honors lose all their charm once the soul has tasted God. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
Really, everything in this world will someday break down, decay, or die. God remains, His angels and saints remain, Heaven remains, hell with its demons and tortures remain, and so does our soul. These things are everlasting. Everything else is - in reality - vanity.
Vanity of vanities! All things are vanity! [Ecclesiastes 1:2]
Prayer reveals to souls the vanity of earthly goods and pleasures. It fills them with light, strength and consolation; and gives them a foretaste of the calm bliss of our heavenly home. [St. Rose of Viterbo]
6. It detaches us from the world.
Mental prayer teaches us to make no account of the world's promises or threats, of its esteem of its contempt; for the world can neither make us happy nor virtuous; we are no better because it extols us to the clouds, nor any worse when it tramples us under foot. We are worth what we are worth in God's eyes...Mental prayer makes us understand that God alone is to be considered... [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
In the end, mental prayer leads us to a great interior freedom. A person who is praised or persecuted, becomes rich or becomes poor, will remain at peace and in contentment because such a soul realizes that it is God alone that matters. What freedom!
7. It detaches us from ourselves.
Our own pride and sensuality substitutes the spirit for the flesh, the soul's delight for bodily pleasures. If there is any fact evident in the history of Christian and religious life, it is that the love of mortification keeps pace in a soul with a love for mental prayer...They bear pains and afflictions, whenever they may come, without a murmur, and even with joy. [The Ways of Mental Prayer, Rt. Rev. Dom Vitalis Lehodey]
This means that the more we practice mental prayer well, the more willing we become to die to ourselves - our own wills, our own plans, our selfishness, and our preferences. We become willing to be detached even from our own perspective on things and it makes us docile to the light of the Holy Spirit and God's perspective on matters. Instead of choosing oneself, one chooses God and His Will. This does not mean we won't struggle doing this day-in and day-out as we battle our sins and various temptations...but if one thing is clear, we want God and His Will alone. Rather than loving self to the contempt of God, one loves God to the contempt of self. And we become set free, degree by degree, from all the things that hold us back from this as God shines His light upon our areas of darkness!
8. Mental prayer unites us to God.
And this is the object of our prayer and reason we pray: To be united with Him, for His glory! The soul grows in intimacy with God as she matures through prayer, the practice of virtue, mortification and suffering. The intimacy we are all called to is the heights of mystical contemplation, which St. Teresa of Avila calls "spiritual marriage." (Note: This is not the same meaning we often hear when the word contemplation is used; for there is natural contemplation as when one gets caught up gazing at a beautiful sunset and there is, for example, theological contemplation wherein we ponder a certain truth and upon understanding it a bit more, we pause in awe at what it means and its beauty). Spiritual marriage is union with God is the closest possible one can attain here on earth, yet it still falls short of the beatific vision of Heaven.
Recap of the eight effects of mental prayer:
1. It enlightens our understanding.
2. It puts to flight our spiritual sloth and lukewarmness.
3. It gives us true self-knowledge.
4. It detaches us from sin.
5. It detaches us from temporal things.
6. It detaches us from the world.
7. It detaches us from ourselves.
8. It unites us to God.
If you have not yet practiced mental prayer (or mental prayer regularly), I want to tell you that your flesh will rebel against this! You may feel the desire the first few times, but then those consolations will be taken away as your faith and loyalty to God become tested and purified. You might realize that sometimes you don't feel like praying. You will be tempted to justify distractions from your time of prayer and before you know it, this daily practice you set out upon will slip away. You'll hear the voice of the enemy telling you "It's so boring" or "It's arduous work" (because it certainly is a laborious task!)...but the enemy's voice will discourage you away from it. You will face distraction after distraction during prayer as you "retrain" your body and mind to choose what is good, right, just, and holy. When you are faced with distraction, think nothing of it and when you realize your mind is wandering, simply turn your thoughts back to God and your meditation. Even if you are doing this the whole time you pray, your time is well-spent and pleasing in the eyes of God! Know too, that when we are faced with distractions in prayer, it is our pride that causes us to get frustrated. Don't get frustrated. Just orient your heart back towards the Lord. Yes, your flesh will repel the self-discipline that a commitment to prayer takes. It truly takes a strong person to do this and that strength can only come from the Lord.
You have no choice but to either stop the fight to pray daily or override your feelings and choose to pray. It will involve an act of your will despite how you feel about it. Why? Because it is right and just and is necessary for your sanctification. AND, when we do this contrary to how we feel in that moment, God pours forth upon us even more graces. Consequently, the more one prays, the more one wants to pray and will go to great lengths and measures to be sure that this time is spent with the Lord each day.
And, even if you do fall away from the discipline of daily mental prayer, nothing matters more than getting back up and continuing to persevere!
I'm going to end this with a quote from St. Bonaventure...
If you would suffer with patience the adversities and miseries of this life, be a man of prayer.
If you would obtain courage and strength to conquer the temptations of the enemy, be a man of prayer.
If you would mortify your own will with all its inclinations and appetites, be a man of prayer.
If you would know the wiles of Satan and unmask his deceits, be a man of prayer.
If you would live in joy and walk pleasantly in the ways of penance, be a man of prayer.
If you would banish from your soul the troublesome flies of vain thoughts and cares, be a man of prayer.
If you would nourish your soul with the very sap of devotion, and keep it always full of good thoughts and good desires, be a man of prayer.
If you would strengthen and keep up your courage in the ways of God, be a man of prayer.
In fine, if you would uproot all vices from your soul and plant all virtues in their place, be a man of prayer.
It is in prayer that we receive the unction and grace of the Holy Spirit, who teaches all things.
I say more: If you would raise yourself to the heights of contemplation and enjoy the sweet embraces of the Spouse, practice mental prayer. It is the way by which the soul is raised to the contemplation and enjoyment of heavenly things.
~ St. Bonaventure, as quoted by St. Peter of Alcantara