The Encheiridion, or Manual (18-20)

When a raven has croaked inauspiciously, let not the appearance hurry you away with it; but straightway make a distinction in your mind and say, None of these things is signified to me, but either to my poor body, or to my small property, or to my reputation, or to my children or to my wife: but to me all significations are auspicious if I choose. For whatever of these things results, it is in my power to derive benefit from it.

You can be invincible, if you enter into no contest in which it is not in your power to conquer. Take care then when you observe a man honoured before others or possessed of great power or highly esteemed for any reason, not to suppose him happy, and be not carried away by the appearance. For if the nature of the good is in our power, neither envy nor jealousy will have a place in us. But you yourself will not wish to be a general or senator (πρύτανις) or consul, but a free man: and there is only one way to this, to despise (care not for) the things which are not in our power.

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