A great effort and much toil are needed in prayer before we can reach a state in which our mind is no longer troubled, and so attain the inward heaven of the heart where Christ dwells. As St. Paul says, 'Do you not realize that Christ dwells within you, unless you are worthless?' (cf. 2 Cor. 13:5).
When someone is beginning the spiritual life, he should not study a lot, but instead watch himself and guard his thoughts. A strong person is the one who chews well, not the one who eats a lot.
True repentance consists of withdrawing from sin and nurturing hatred for it. For, lo, when someone says from his heart: I have hated deceit and been repelled by it - then God accepts him with joy.
The head of every good striving and the pinnacle of all corrections is to persevere in prayer, by which we may ever obtain, through entreaty of God, all the other virtues as well. By prayer those who are worthy partake of the sanctity of God and spiritual activity and the union of the mind with the Lord in unutterable love. He who constantly forces himself to endure in prayer is roused by spiritual love to Divine fervor and flaming desire towards God, and he receives, according to his measure, the grace of spiritual, sanctifying perfection.
Do not pray that things may be according to your desires, for they are not always in keeping with the will of God. Better pray as you were taught, saying: ‘Thy will be done’ on me (Matt. vi 10). And ask thus about all things, for He always desires what is good and profitable for your soul, whereas you do not always seek it.
Prayer is a great good if offered up from a thankful soul; if we are steadfast in it, so that whether we receive or do not receive what we pray for we at all times give thanks to God. For since He will sometimes grant what we ask and sometimes will not, in both cases it is to our gain... For oftentimes God will delay, not as denying our prayer, but in His wisdom seeking rather for our perseverance, and desiring to draw us nearer to Himself; as a loving father when asked by his son for something will often do; withholding consent, and not from the will to refuse, but rather to encourage him in steadfastness.
It is always possible to make a new start by means of repentance. 'You fell,' it is written, 'now arise'(cf. Prov. 24:16). And if you fall again, then rise again, without despairing at all of your salvation, no matter what happens. So long as you do not surrender yourself willingly to the enemy, your patient endurance, combined with self-reproach, will suffice for your salvation. 'For at one time we ourselves went astray in our folly and disobedience,' says St. Paul. '... Yet He saved us, not because of any good things we had done, but in His mercy' (Tit. 3:3,5).
The most important thing in any good effort and the height of all activities is to persevere in prayer, by means of which we can always acquire through supplication the other virtues from God as well.
You describe how bitterly you regret the inefficacy of your prayers. Beware: to wish for consolation or revelation in prayer is a sure sign of pride. Pray humbly, in perfect simplicity, seeking salvation only through forgiveness, & having faith that God will extend to you His mercy - as He did to the publican.
No Christian believing rightly in God should ever be off his guard. He should always be on the look-out for temptation, so that when it comes he will not be surprised or disturbed, but will gladly endure the toil and affliction it causes, and so will understand what he is saying when he chants with the prophet: 'Prove me, O Lord, and try me' (Ps. 26:2 LXX). For the prophet did not say, 'Thy correction has destroyed me,' but, 'it has upheld me to the end' (Ps. 18:35 LXX).
Habit forms from custom, and habit seems to accustom itself to nature. It is much worse and more difficult to change nature. However, with God it is possible. For nature does not set itself against God.
O man, learn the humility of Christ and the Lord will give you to taste of the sweetness of prayer. And if you would pray cleanly, be humble and temperate, confess yourself thoroughly, and prayer will feel at home in you. Be obedient, submit with a good conscience to those in authority; be content with all things, and your mind will be cleansed of vain thoughts. Remember that the Lord sees you, and be fearful lest you anywise offend your brother, whom neither dispraise nor grieve, even by a look, and the Holy Spirit will love you and will Himself be your help in all things.
Wherever we are and whatever our circumstances, the enemy always tries to prevent us from actively responding to the call. Pray for help. For help that you may never fail to respond. And beware lest, having received help and having done the right deed because of it, you should grow proud and acquire the habit of condemning others, in the secret chambers of your heart. Beware! For this would make all the fruits of your good works wither.
Pray simply. Do not expect to find in your heart any remarkable gift of prayer. Consider yourself unworthy of it. Then you will find peace. Use the empty cold dryness of your prayer as food for your humility. Repeat constantly: I am not worthy; Lord, I am not worthy! But say it calmly; without agitation.
When we return to prayer after a period of reading we find a rejuvenated and invigorated soul, stirred by the desire for God. The best form of prayer is one that implants the clearest idea of God in the soul and thus makes space for the presence of God within us. We become a temple of God when our continuous meditation on Him is not constantly interrupted by ordinary worries, and the spirit is not disturbed by unexpected emotions. Thus, in flight from all things, the spirit who loves God can approach God who drives out everything that leads us to evil, and holds steadfastly to everything that leads to virtue.