On Anger, Book 3, Section 12 — In Plain English

Seneca — The Senator

So Plato refused to use his authority over his own servants. Once, when he was angry about some mistake, he said, "Speusippus, please punish that slave for me. I'm too angry right now." He wouldn't strike the slave for the exact reason another person would have struck him. "I'm in a rage," he said. "I would beat him harder than I should. I would enjoy it more than I should. Don't let that slave suffer under someone who can't control himself." Do you really want to give an angry person the power of revenge, when even Plato gave up his own right to use it? When you're angry, you shouldn't be allowed to do anything. "Why?" you ask. Because when you're angry, there's nothing you don't want permission to do.

Seneca — The Senator Original

He therefore denied himself the exercise of authority over his own household, and once, being rather angry at some fault, said, "Speusippus, will you please to correct that slave with stripes; for I am in a rage." He would not strike him, for the very reason for which another man would have struck him. "I am in a rage," said he; "I should beat him more than I ought: I should take more pleasure than I ought in doing so: let not that slave fall into the power of one who is not in his own power." Can any one wish to grant the power of revenge to an angry man, when Plato himself gave up his own right to exercise it? While you are angry, you ought not to be allowed to do anything. "Why?" do you ask? Because when you are angry there is nothing that you do not wish to be allowed to do.