Embittered and furious…

If we take St Paul literally, then we are not allowed to cling to our anger for even a day (cf. Eph 4.26). I would like to make a comment, however, that many people are so embittered and furious when they are in a state of anger, that they not only cling to their anger for a day, but drag it on for weeks. I am at a loss for words to explain those who do not even vent their anger in speech but erect a barrier of sullen silence around them and distill the bitter poison of their hearts until it finally destroys them.
— Saint John Cassian (c. 360-435)

Anger makes us…

This deadly cancer of anger from which so much harm grows: it makes us unlike ourselves, makes us like timberwolves or furies from Hell, drives us forth headlong upon the points of swords, makes us blindly run forth after other men’s destruction as we hasten toward our own ruin.
— Saint Thomas More (1478-1535)

To avoid dissensions…

To avoid dissensions we should be ever on our guard, more especially with those who drive us to argue with them, with those who vex and irritate us, and who say things likely to excite us to anger. When we find ourselves in company with quarrelsome, eccentric individuals, people who openly and unblushingly say the most shocking things, difficult to put up with, we should take refuge in silence, and the wisest plan is not to reply to people whose behavior is so preposterous.
— Saint Ambrose of Milan (339-397)