Just as scurvy is a disease of the body, so anger is a disease of the soul. Observe that most people, when they persist in their anger, do not pay attention to what they do, and they do many things in their anger that they would not do otherwise. For anger deprives man of his reasoning, and he becomes even angrier and enters into dispute and recrimination. Therefore it is impossible for the angry man to escape great sins. The man of anger does not overlook things and does not forgive his insult, but he is always vengeful and grudging.
Anger brings one to contention.
The angry man will not be very wise, for anger drives wisdom from one's heart, so that he will not be able to answer correctly or to reprove correctly, and none of his words will be reasonable. The angry man hardens himself to reproof and chastisement, for no one is allowed to reveal to him his mistakes and his ugly ways. And withholding of wrath is one of the thirteen attributes stated in relation to the Blessed Creator.