We are made up of a soul and body, and both soul and body consist of many members. For the soul too has members after a fashion: those parts of it concerned with growth, desiring, anger and reason. Therefore, true fasting must extend to every part, cleansing and healing them all. Fasting, brethren, gently and kindly restores the soul to health, and that is why our Fathers imposed it on us during these days.
—St. Gregory Palamas
Man cannot drive away impassioned thoughts unless he watches over his desire… He destroys desire through fasting, vigils and sleeping on the ground… through long-suffering, forbearance, forgiveness and acts of compassion… It is impossible to overcome these passions unless we can rise above attachment to food and possessions, to self-esteem and even to our very body, because it is through the body that the demons often attempt to attack us.
—Evagrios the Solitary
Let us vie with each other in observing the purity of the fast (1 Cor. 9:24-27), by watchfulness in prayers, by study of the Scriptures, by distributing to the poor, and let us be at peace with our enemies. Let us bind up those who are scattered abroad, banish pride, and return to lowliness of mind, being at peace with all men, and urging the brethren unto love. Thus also the blessed Paul was often engaged in fastings and watchings, and was willing to be accursed for his brethren. Blessed David again, having humbled himself by fastings, used boldness, saying, “O Lord my God, if I have done this, if there is any iniquity in my hands, if I have repaid those who dealt evil with me, then may I fall from my enemies as a vain man.” If we do these things, we shall conquer death; and receive an earnest of the kingdom of heaven.
—St. Athanasius the Great
Fasting is a good teacher: (1) It soon makes everybody who fasts understand that a man requires very little food and drink, and that in general we are greedy and eat a great deal more than is necessary– that is, than our nature requires. (2) Fasting clearly shows or discloses all the infirmities of our soul, all its weaknesses, deficiencies, sins, and passions; just as when muddy, standing water is beginning to be cleaned it shows what reptiles and what sort of dirt it contains. (3) It shows us all the necessity of turning to God with the whole heart, and of seeking His mercy, help, and salvation. (4) Fasting shows all the craftiness, cunning, and malice of the bodiless spirits, whom we have hitherto unwittingly served, and whose cunning, now that we are enlightened by the light of God’s grace, becomes clear, and who now maliciously persecute us for having left their ways.
—St. John of Kronstadt
Bodily fasting alone is not enough to bring about perfect 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 everything 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, murders, adulteries, unchastity” and so on (Matthew 15:19). We are told to fast not only to mortify our body, but also to keep our intellect watchful, so that it will not be obscured because of the amount of food we have eaten and thus be unable to guard its thoughts. We must not therefore expend all our effort in bodily fasting; we must also give attention to our thoughts and to spiritual meditation, since otherwise we will not be able to advance to the heights of true purity and chastity. As our Lord has said, we should “cleanse first the inside of the cup and plate, so that their outside may also be clean” (Matt. 23:26).
—St. John Cassian
Through His incarnation God gave us the model for a holy life and recalled us from our ancient fall. In addition to many other things. He taught us, feeble as we are, that we should fight against the demons with humility, fasting, prayer and watchfulness. For when, after His baptism, He went into the desert and the devil came up to Him as though He were merely a man, He began His spiritual warfare by fasting and won the battle by this means — though being God, and God of gods. He had no need of any such means at all.
—St. Hesychios the Priest