Whatever a man loves, he desires at all costs to be near to continuously and uninterruptedly, and he turns himself away from everything that hinders him from being in contact and dwelling with the object of his love. It is clear therefore that he who loves God also desires always to be with him and to converse with him. This comes to pass in us through pure prayer. Accordingly, let us apply ourselves to prayer with all our power; for it enables us to become akin to God. Such a man was he who said: “O God, my God, I cry to Thee at dawn; my soul has thirsted for Thee” (Psalm 63:1, LXX). For the man who cries to God at dawn has withdrawn his intellect from every vice and clearly is wounded by divine love. St. Theodoros the Great Ascetic II, A Century of Spiritual Texts, sec. 94”
Our Lord tells us there is more joy in heaven over one sinner who repents than over ninety nine others who have no need of repentance. It may seem strange to us to imagine the existence of such a joy, especially in regard to ourselves. Perhaps very few of us allow ourselves to weep true tears of repentance, to experience true sorrow for our sins, and so never come to know that heavenly joy. Tears that emerge from eyes that gaze upon Christ are the prelude to the loving embrace of the Heavenly Bridegroom. If there is one thing the devil would want to prevent it is this movement from sorrow to joy, from repentance to intimacy. He would keep us in the despair of our own wretchedness, despondent through lack of hope in forgiveness or convince us that our sins are of no account - such that our repentance produces no tears, internal or external. In both cases, we see only the light of salvation fade and the heart grow cold.
Let us not then make ourselves unworthy of entrance into the bride-chamber: for as long as we are in this world, even if we commit countless sins it is possible to wash them all away by manifesting repentance for our offenses: but when once we have departed to the other world, even if we display the most earnest repentance it will be of no avail, not even if we gnash our teeth, beat our breasts, and utter innumerable calls for succor, no one with the tip of his finger will apply a drop to our burning bodies, but we shall only hear those words which the rich man heard in the parable ‘Between us and you a great gulf has been fixed.’ [Luke xvi. 26]
Let us then, I beseech you, recover our senses here and let us recognize our Master as He ought to be recognized. For only when we are in Hades should we abandon the hope derived from repentance: for there only is this remedy weak and unprofitable: but while we are here even if it is applied in old age itself it exhibits much strength. Wherefore also the devil sets everything in motion in order to root in us the reasoning which comes of despair: for he knows that if we repent even a little we shall not do this without some reward. But just as he who gives a cup of cold water has his recompense reserved for him, so also the man who has repented of the evils which he has done, even if he cannot exhibit the repentance which his offenses deserve, will have a commensurate reward. For not a single item of good, however small it may be, will be overlooked by the righteous judge. For if He makes such an exact scrutiny of our sins, as to require punishment for both our words and thoughts, much more will our good deeds, whether they be great or small, be reckoned to our credit at that day.
Wherefore, even if thou art not able to return again to the most exact state of discipline, yet if thou withdraw thyself in a slight degree at least from thy present disorder and excess, even this will not be impossible: only set thyself to the task at once, and open the entrance into the place of contest; but as long as thou tarriest outside this naturally seems difficult and impracticable to thee. [Matt. xxv. 34; 249 Luke xvi. 26]. For before making the trial even if things are easy and manageable they are wont to present an appearance of much difficulty to us: but when we are actually engaged in the trial, and making the venture the greater part of our distress is removed, and confidence taking the place of tremor and despair lessens the fear and increases the facility of operation, and makes our good hopes stronger.
For this reason also the wicked one dragged Judas out of this world lest he should make a fair beginning, and so return by means of repentance to the point from which he fell. For although it may seem a strange thing to say, I will not admit even that sin to be too great for the succor which is brought to us from repentance. Wherefore I pray and beseech you to banish all this Satanic mode of thinking from your soul, and to return to this state of salvation.
+ St. John Chrysostom, An Exhortation to Theodore After His Fall, Letter 1
Our exposure to sin can coarsen our hearts over time and we can become insensitive to the pleas of Divine Love. The fathers teach that the heart, therefore, must be broken. It must be shattered, but not in a violent fashion. Rather, it is through prayer, especially through vigils - when the mind and body have been humbled - that true compunction emerges. The heart is shattered through the knowledge of one's sins in the face of the love of God and His desire for the soul. This sorrow opens the door to the heart. “To brood on evil makes the heart brazen; but to destroy evil through self-restraint and hope breaks the heart. There is a breaking of the heart that is gentle and makes it deeply penitent, and there is a breaking that is violent and harmful, shattering it completely. Vigils, prayer, and patient acceptance of what comes constitute a breaking that does not harm but benefits the heart, provided we do not destroy the balance between them through excess. He who perseveres in them will be helped in other ways as well; but he who is slack and negligent will suffer intolerably on leaving this life. A self-indulgent heart becomes a prison and chain for the soul when it leaves this life; whereas an assiduous heart is an open door. St. Mark the Ascetic”
Cassian, the great teacher that he is, makes it clear that both internal and external disciplines are needed in the spiritual life and the quest for purity of heart. Above all, humility stands above all the rest because it leads us to distrust the self and place ourselves completely in the care of the "Doctor of our souls." Bodily fasting alone is not enough to bring about self-restraint and true purity; it must be accompanied by contrition of heart, intense prayer to God, frequent meditation on the Scriptures, toil, and manual labor. These are able to check the restless impulses of the soul and to recall it from its shameful fantasies. Humility of soul helps more than anything else, however, and without it no one can overcome unchastity or any other sin. In the first place, then, we must take the utmost care to guard the heart from base thoughts, for, according to the Lord, “Out of the heart proceed evil thoughts, murder, adulteries, unchastity, and so on” (Matthew 15:19). The Doctor of our souls has also placed the remedy in the hidden regions of the soul, recognizing that the cause of our sickness lies there when he says: “Whoever looks at a woman with lust has already committed adultery with her in his heart” (Matthew 5:28). He seeks to correct not so much our inquisitive and unchaste eyes as the soul that has its seat within and makes bad use of the eyes that God gave it for good purposes. That is why the book of Proverbs in its wisdom does not say, “Guard your eyes with all diligence” but “Guard your heart with all diligence” (Proverbs 4:23), imposing the remedy of diligence in the first instance upon that which makes use of the eyes for whatever purpose it desires. St. John Cassian I, On the Eight Vices”
Watchfulness of heart must be constant because the demons never sleep and are relentless to gain possession of what belongs to God alone. We must keep a guard over our senses, in particular, given the fact that through them we are in a constant state of receptivity. Once one is able to discern the true nature of his thoughts and how they defile, he can remain calm and peaceable even in the midst of attacks. However, no matter what level of discernment we may have achieved, the battle remains until the end of our lives. We must have no confidence in ourselves but cast ourselves upon the mercy of God. The demons cunningly withdraw for a time in the hope that we will cease to guard our heart, thinking we have now attained peace; then they suddenly attack our unhappy soul and seize it like a sparrow. Gaining possession of it, they drag it down mercilessly into all kinds of sin, worse than those that we have already committed and for which we have asked forgiveness. Let us stand, therefore, with fear of God and keep guard over our heart, practicing the virtues that check the wickedness of our enemies. Stand guard, then, over your heart and keep watch on your senses; and if the remembrance of God dwells peaceably within you, you will catch the thieves when they try to deprive you of it. When a man has an exact knowledge about the nature of thoughts, he recognizes those that are about to enter and defile him, troubling the intellect with distractions and making it lazy. Those who recognize these evil thoughts for what they are remain undisturbed and continue in prayer to God. I entreat you not to leave your heart unguarded, as long as you are in the body. Just as a farmer cannot feel confident about the crop growing in his fields, because he does not know what will happen to it before it is stored away in his granary, so a man should not leave his heart unguarded as long as he still has breath in his nostrils. Up to his last breath he cannot know what passion will attack him; as long as he breathes, therefore, he must not leave his heart unguarded, but should at every moment pray to God for his help and mercy. St. Isaiah the Solitary
Cassian takes up the theme of the three sources of one's calling to the monastic life or to conversion (God, the example of others, need) and the three types of renunciation essential for living a life of deep conversion (detachment from worldly goods, one's passions, and from all things that prevent theoria or contemplation.) Discussion ensued about compunction, conversion in one's daily life, and embracing a spirit of renunciation in the modern world.
Through holy baptism we are granted remission of our sins, are freed from the ancient curse, and are sanctified by the presence of the Holy Spirit. But we do not as yet receive the perfection of grace … for that is true only of those who are steadfast in faith and have demonstrated this through what they do. If after we have been baptized we gravitate toward evil and foul actions, we lose the sanctification of baptism completely. But through repentance, confession, and tears we receive a corresponding remission of our former sins and, in this way, sanctification accompanied by the grace of God. St. Symeon the New Theologian