Saint Augustine, The City of God, Vol. II

Therefore, for him, foolishness was the cause even of this useful and desirable sadness, by which a man grieves that he is what he ought not to be. The Stoics, however, say that it is not the fool, but the wise man who cannot be sad.

CHAPTER IX.

Concerning the perturbations of the soul, whose right affections the life of the just possesses.

But we have already answered these philosophers regarding this question of the perturbations of the soul in the ninth book of this work, showing that they are more eager for contention over words than for truth regarding the things themselves. Among us, however, according to the Holy Scriptures—that is, sound doctrine—the citizens of the holy city of God, living according to God in the pilgrimage of this life, fear and desire, grieve and rejoice; and because their love is right, they possess all these affections rightly. They fear eternal punishment; they desire eternal life. They grieve in their current state, because they still groan within themselves, awaiting the adoption, the redemption of their body; they rejoice in hope, because the word that is written will come to pass: Death is swallowed up in victory. Likewise, they fear to sin; they desire to persevere. They grieve for their sins; they rejoice in good works. For in order that they may fear to sin, they hear: Because iniquity shall abound, the love of many shall grow cold; in order that they may desire to persevere, they hear what is written: He that shall persevere to the end, he shall be saved; in order that they may grieve for their sins, they hear: If we say that we have no sin, we deceive ourselves, and the truth is not in us; in order that they may rejoice in good works...