For as a bright sunny day and winter with all its gloom, so are the soul of the angry and that of the gentle. However, let us at present look not to the mischievous consequences resulting to others, but to those which affect the persons themselves: though indeed it is also no slight mischief (to one's self) to cause ill to another, for the present, however, let that be the consideration. What executioner with his lash can so lacerate the ribs, what red-hot lancets (ὀ βελίσκοι) ever so pierced the body, what madness can so dispossess a man of his natural reason, as anger and rage do?
I know many instances of persons engendering diseases by giving loose to anger: and the worst of fevers are precisely these. But if they so injure the body, think of the soul. For do not argue that you do not see the mischief, but rather consider, if that which is the recipient of the malignant passion is so hurt, what must be the hurt sustained by that which engenders it! Many have lost their eyes, many have fallen into most grievous disease. Yet he that bears bravely, shall endure all things easily.
But, however, both such are the troublesome tasks the devil enjoins, and the wages he assigns us for these is hell. He is both devil and foe to our salvation, and we rather do his bidding than Christ's, Saviour as He is, and Benefactor and Defender, and speaking as He does such words, which are both sweeter, and more reverend, and more profitable and beneficial, and are both to ourselves and to those who live in our company the greatest of blessings. Nothing worse than anger, my beloved, nothing worse than unseasonable wrath.
It will not have any long delay; it is a quick, sharp passion. Many a time has a mere word been blurted out in anger, which needs for its curing a whole lifetime, and a deed been done which was the ruin of the man for life. For the worst of it is this, that in a little moment, and by one act, and by a single word, full oft has it cast us out from the possession of eternal good, and brought to nought a world of pains. Wherefore I beseech you to do all you can to curb this savage beast.
Thus far, however, I have spoken concerning meekness and wrath; if one should take in hand to treat of other opposites, as covetousness and the mad passion for glory, contrasted with contempt of wealth and of glory; intemperance with sobriety; envy with benevolence; and to marshal them each against its opposite, then one would know how great the difference. Behold how from the very things enjoined it is plainly shown, that the one master is God, the other the devil! Why then, let us do God's bidding, and not cast ourselves into bottomless pits; but while there is time, let us wash off all that defiles the soul, that we may attain unto the eternal blessings, through the grace and mercy of our Lord Jesus Christ, with Whom to the Father and Holy Ghost together be glory, power, honor, now and ever, and world without end.
Amen.
Source: Homilies on Acts (New Advent)