One should not ponder divine matters on a full stomach, say the ascetics. For the well-fed, even the most superficial secrets of the Trinity lie hidden.
The reason that fasting has an effect on the spirits of evil rests in its powerful effect on our own spirit. A body subdued by fasting brings the human spirit freedom, strength, sobriety, purity, and keen discernment.
Fasting is an exceptional virtue; it represses bodily impulses and gives strength to the soul to fight against the poisoning of the heart through the senses, and provides it with a remedy against any past poisoning. Fasting causes the mind to be cleansed constantly. It withers up every evil thought and brings healthy, godly thoughts -- -holy thoughts that enlighten the mind and kindle it with more zeal and spiritual fervor.
Fasting is absolutely indispensable for man. From the external aspect, it is a struggle of filial obedience to God, Who has given us the rules of fasting through His Holy Spirit. From the inner aspect, fasting is a struggle of restraint and self-limitation. In this lies the great value and sense of fasting, since a strict observance of fasts tempers one's will and perfects the character of one who is firm in his religious convictions and actions. Let us not forget that Christ Himself fasted, and foretold that His apostles would also fast.
A life of fasting, properly understood as general self-limitation and abstinence, to the annual practice of which the Church always calls us with the Great Lent, is really that bearing of the cross and self-crucifixion which is required of us by our calling as Christians. And anyone who stubbornly resists this, wanting to live a carefree, happy, and free life, is concerned for sensual pleasures and avoids sorrow and suffering, that person is not a Christian. Bearing one's cross is the natural way of every true Christian, without which there is no Christianity.
Fasting is the champion of every virtue, the beginning of the struggle, the crown of the abstinent, the beauty of virginity and sanctity, the resplendence of chastity, the commencement of the path of Christianity, the mother of prayer, the well-spring of sobriety and prudence, the teacher of stillness, and the precursor of all good works. Just as the enjoyment of light is coupled with healthy eyes, so desire for prayer accompanies fasting that is practiced with discernment.
When you fast and are nourished with abstinence, do not store the leftovers for tomorrow, but, as the Lord became poor and enriched us, feed someone who does not want to be hungry, you who hungers willingly. Then your fast will be like the dove who brings and joyfully proclaims salvation to your soul from the flood.
Fasting appears gloomy until one steps into its arena. But begin and you will see what light it brings after darkness, what freedom from bonds, what release after a burdensome life…
In no art do the artists judge the result of their work by the tools they use, but they await the work's completion and by it judge the art. Adopting such a practice with regard to food, not placing all your hope on fasting, but fasting moderately and according to the amount of your strength, strive toward mental activity. In this way you can avoid pride and will not spurn God's good works, sending up praises to God for everything.
God the Word, the God-Man, our Lord Jesus Christ, compares our life with a market, and the work of our life on earth He calls trading, and says to us all: Trade till I come (Luke 19:13), redeeming the time, because the days are evil (Ephesians 5:16). That is to say, make the most of your time for getting heavenly blessings through earthly goods. Earthly goods are good works done for Christ's sake and conferring on us the grace of the All-Holy Spirit.
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.
I shall speak first about control of the stomach, the opposite to gluttony, and about how to fast and what and how much to eat. I shall say nothing on my own account, but only what I have received from the Holy Fathers. They have not given us only a single rule for fasting or a single standard and measure for eating, because not everyone has the same strength; age, illness or delicacy of body create differences. But they have given us all a single goal: to avoid over-eating and the filling of our bellies... A clear rule for self-control handed down by the Fathers is this: stop eating while still hungry and do not continue until you are satisfied.
You know that evil entered into us through the transgression of the commandments. Hence it is obvious that by keeping them, evil departs from us. But without the doing of the commandments we should not even aspire or hope for purity of soul, because at the very outset we do not walk on the path that leads us to purity of soul. Do not say that God can give us the grace of purity of soul even without our keeping the commandments.