As a general rule, decide whether a thing is permissible by the effect it produces within. Permit yourself what is constructive, but never what is destructive.
The kingdom of God is within us when God reigns in us, when the soul in its depths confesses God as its master, and is obedient to Him in all its powers. Then God acts within it as master ‘both to will and to do of his good pleasure’ (Phil. ii. 13). This reign begins as soon as we resolve to serve God in our Lord Jesus Christ, by the grace of the Holy Spirit. Then the Christian hands over to God his consciousness and freedom, which comprises the essential substance of our human life, and God accepts the sacrifice; and in this way the alliance of man with God and God with man is achieved, and the covenant with God, which was severed by the fall and continues to be severed by our willful sins, is re-established. This inner alliance is sealed, confirmed, and given the strength to maintain itself by the power of grace in the divine sacrament of baptism, and for those who have fallen after baptism, in the sacrament of repentance: and afterwards it is constantly strengthened by holy communion. All Christians live thus; and consequently they all bear the kingdom of God within themselves, that is to say they obey God as King and are ruled by God as King.
What do we do when attacked by some criminal? We strike out at him and shout for help. Our cries are answered by the police, who then rescue us from danger. We must do the same in inner warfare with the passions. Filled with anger against them, call for assistance: Help me, O Lord! Jesus Christ, Son of God, save me! O God, make speed to save me! O Lord make haste to help me! Having thus called on the Lord, do not allow your attention to wander from Him, do not let it turn to what is happening within you, but go on standing before the Lord and imploring His help. This will make the enemy run away as though pursued by flames.
The man who does not humble himself and does not cleanse his heart from evil desires fasts in vain. He may eat nothing at all, but it will be to no avail if there is evil inside him. He must first cleanse himself from the evil within in order to receive the Lord.
Set your sight on heaven and order every step of your life so that it will be a step in that direction. It seems to me that it is all so simple, and yet so all-embracing.
The way of Godliness consists of these two things: True (pious) doctrines and good works. Without good works, true faith is not acceptable to God, likewise, good works are not acceptable to Him in the absence of True Faith (pious dogma).
What can God do with one who willfully gives himself over to the world, and is deceived by its pleasures, or led astray by material wanderings? The man to whom He gives help is the one who turns away from material pleasures and from his former habits, who drags his mind at all times to the Lord, whether it will or not, who denies himself and seeks the Lord only. This is the man whom He keeps under His care: who guards himself on every side from the snares and entanglements of the material world, who works out his own salvation with fear and trembling, who passes with all heed amidst the snares and entanglements and lusts of this world, and seeks the help of the Lord, and hopes by His mercy to be saved through grace.
You must set about rooting out the very desire to have things pleasant, to get on well, to be contented. You must learn to like sadness, poverty, pain, hardship. You must learn to follow privately the Lord's bidding: not to speak empty words, not to adorn yourself, always to obey authority, not to look at a woman with desire, not to be angry and much else. For all these biddings are given us not in order for us to act as if they did not exist, but for us to follow: otherwise the Lord of mercy would not have burdened us with them. If any man will come after me, let him deny himself, He said (Matthew 16:24), thereby leaving it to each person's own will ... and to each person's endeavor: let him deny himself.
In the beginning there are a great many battles and a good deal of suffering for those who are advancing towards God and afterwards, ineffable joy. It is like those who wish to light a fire; at first they are choked by the smoke and cry, and by this means obtain what they seek -- as it is said, 'Our God is a consuming fire' -- so we also must kindle the divine fire in ourselves through tears and hard work.
To the world belong our desires and impulses. enumerates them: Weakness for wealth and for collecting and owning things of different kinds; the urge for physical (sensuous) enjoyment; the longing for honor, which is the root of envy; the desire to conquer and be the deciding factor; pride in the glory of power; the urge to adorn oneself and to be liked; the craving for praise; concern and anxiety for physical well-being. All these are of the world; they combine deceitfully to hold us in heavy bonds. If you wish to free yourself, scrutinize yourself with the help of that list and see clearly what you have to struggle against in order to approach God. For friendship with the world is enmity with God, and whosoever therefore will be a friend of the world is the enemy of God (James 4:4).
Even if a person’s sin is not only obvious, but very grievous and comes from a hardened and unrepentant heart, do not condemn him, but raise your eyes to the wondrous and incomprehensible judgments of God; then you will see that many people, formerly full of iniquity, later repented and reached a high degree of sanctity, and that, on the other hand, others, who were on a high level of perfection, fell into a deep abyss. Take care, lest you also suffer this calamity through judging others.
Fasting is acceptable to God when abstention from food is accompanied by refraining from sins, from envy, from hatred, from calumny, from vainglory, from wordiness, from other evils. He who is fasting the true fast `that is agreeable' to God ought to shun all these things with all his strength and zeal, and remain impregnable and unshakeable against all the attacks of the evil one that are planned from that quarter. On the other hand, he who practices abstention from food, but does not keep self-control in the face of the aforesaid passions, is like unto one who lays down splendid foundations for a house, yet takes serpents and scorpions and vipers as fellow-dwellers therein.
The Holy Fathers recommend 'moderate' fasting; one ought not to allow the body to be weakened too much, for then the soul, too, is harmed. Nor ought one to undertake fasting too suddenly; everything demands practice, and each one should look to his own nature and occupation. To choose among different kinds of food is to be condemned; all food is God-given, but it is advisable to avoid such kinds as add to the body's weight and appetite; strong spices, meat, spirituous drinks and such foods as are solely for the palate's enjoyment. For the rest, one may eat what is cheap and most easily available, they say. But by 'moderate' they mean one meal a day, and that one light enough not to fill the stomach to satiety.
Inside us evil is at work suggesting unworthy inclinations. However, it is not in us in the same way as, to take as an example, water mixes with wine. Evil is in us without being mixed with good. We are a field in which wheat and weeds are growing separately. We are a house in which there is a thief, but also the owner. We are a spring which rises from the middle of the mud, but pours out pure water. All the same, it is enough to stir up the mud and the spring is fouled. It is the same with the soul. If the evil is spread, it forms a unity with the soul and makes it dirty. With our consent, evil is united with the soul; they become accomplices. Yet there comes a moment when the soul can free itself and remain separate again: in repentance, contrition, prayer, recourse to God. The soul could not benefit from these habits if it were always sunk in evil. It is like a marriage. A woman is united with a man and they become one flesh. But when one of them dies, the other is left alone. But union with the Holy Spirit is complete. So, let us become a single spirit with Him. Let us be wholly absorbed by grace.