How to seek for discretion.
We ought then with all our might to strive for the virtue of discretion by the power of humility, as it will keep us uninjured by either extreme, for there is an old saying ἀκρότητες ἰσότητες, i.e., extremes meet. For excess of fasting and gluttony come to the same thing, and an unlimited continuance of vigils is equally injurious to a monk as the torpor of a deep sleep: for when a man is weakened by excessive abstinence he is sure to return to that condition in which a man is kept through carelessness and negligence, so that we have often seen those who could not be deceived by gluttony, destroyed by excessive fasting and by reason of weakness liable to that passion which they had before overcome. Unreasonable vigils and nightly watchings have also been the ruin of some whom sleep could not get the better of: wherefore as the apostle says “with the arms of righteousness on the right hand and on the left,” 1196 we pass on with due moderation, and walk between the two extremes, under the guidance of discretion, that we may not consent to be led away from the path of continence marked out for us, nor fall by undue carelessness into the pleasures of the palate and belly.
2 Cor. vi. 7.