The Enchiridion (Version 2) 20 : 1

Remember that it is not he who reviles you or strikes you, who insults you, but it is your opinion about these things as being insulting. When, then, a man irritates you, you must know that it is your own opinion which has irritated you. Therefore especially try not to be carried away by the appearance. For if you once gain time and delay, you will more easily master yourself.