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.
A small affliction borne for God's sake is better [before God] than a great work performed without tribulation, because affliction willingly borne brings to light the proof of love.
Just as we must beware of overeating, so too we must beware of excessive temperance or abstinence. Excessive temperance weakens the body, destroys wakefulness, coolness and freshness which are indispensable for vigilance, and which fade and weaken when the physical powers succumb and fail. If you force a weak body to labor beyond its powers, you subject your soul to double darkness, and lead it into confusion (and not relief)...
Temptations are sent for improvement when God delivers his righteous ones to various temptations, humiliating them for some slight and unimportant offense, or to increase their purity, in order that every uncleanliness of thought, or... dross which He sees they have harbored in secret, may be burnt away in this present life, and that so He may bring them, as it were pure gold, to the future judgment...
One must by every means strive to preserve peace of soul and not be disturbed by offenses from others; for this one must in every way strive to restrain anger and by means of attentiveness to keep the mind and heart from improper feelings. And therefore we must bear offenses from others with equanimity and accustom ourselves to such a disposition of spirit that these offenses seem to concern not us, but others. Such a practice can give quietness to the human heart and make it as dwelling for God Himself.
Sometimes, when we are overcome by pride or impatience and are unwilling to amend our ill-conditioned and disordered way of life, we complain that what we need is solitude, as though in solitude, meeting with no provocation, we should find there the virtue of patience, making excuses for our slackness, and laying the blame of our agitation not upon our own lack of patience, but ascribing it to the faults of our brethren, whereas so long as we impute to others the causes of our own faults, we shall never be able to reach the goal of patience and of perfection.
Fasts and vigils, the study of Scripture, renouncing possessions and everything worldly are not in themselves perfection, as we have said; they are its tools. For perfection is not to be found in them; it is acquired through them. It is useless, therefore, to boast of our fasting, vigils, poverty, and reading of Scripture when we have not achieved the love of God and our fellow men. Whoever has achieved love has God within himself and his intellect is always with God.
A small affliction borne for God’s sake is better [before God] than a great work performed without tribulation, because affliction willingly borne brings to light the proof of love.
A righteous person who is wise resembles God: he never disciplines anyone in order to take vengeance upon a wrongdoing, but only so that the person may be set aright, or that others may be deterred.
The virtues follow one from another in succession, so that the path of virtue does not become grievous and burdensome, and so that by being achieved in order progressively they may be made light; thus the hardships endured for virtue's sake should be cherished by a man as is the good itself.
No virtue makes flesh-bound man so like a spiritual angel as does self-restraint, for it enables those still living on earth to become, as the Apostle says, 'citizens of heaven' (cf. Phil. 3:20).
Of the Only Case in Which Anger is Good... But we have a use for anger most properly planted within us, and for this use alone it is profitable and healthful for us to entertain it, namely, when we burn with wrathful indignation against the lustful motions of our own hearts, and are enraged to find that those things which we should be ashamed to do or to speak of before men have found admittance into the secret places of our minds. We may then well dread and fear exceedingly the presence of the Angels and the Omnipresence of God Himself, and His all-seeing Eye from which no secrets of our hearts can lie hid.