You shouldn't believe him even if he promises, "I'll never do it again." He will sin, and others will sin against him. He'll spend his whole life wallowing in evil. You must meet cruelty with kindness. When dealing with an angry person, use the same argument that works so well with someone who's grieving: "Will you ever stop this, or never? If you're going to stop someday, isn't it better to abandon anger before anger abandons you? Or will this fury never leave you? Do you see what a restless life you're condemning yourself to? What kind of life can someone have who's always boiling with rage?" Here's another point: even after you've worked yourself into a fury and kept finding new reasons to stay angry, your anger will eventually leave on its own. Time will drain its strength. How much better, then, to defeat it yourself rather than let it defeat itself?
Why, you should not believe him even if he said, “Never will I do so again.” He will sin, and another will sin against him, and all his life he will wallow in wickedness. Savagery must be met by kindness: we ought to use, to a man in anger, the argument which is so effective with one in grief, that is, “Shall you leave off this at some time, or never? If you will do so at some time, how better is it that you should abandon anger than that anger should abandon you? Or, will this excitement never leave you? Do you see to what an unquiet life you condemn yourself? for what will be the life of one who is always swelling with rage?” Add to this, that after you have worked yourself up into a rage, and have from time to time renewed the causes of your excitement, yet your anger will depart from you of its own accord, and time will sap its strength: how much better then is it that it should be overcome by you than by itself?