Meditations by Marcus Aurelius

Say to yourself first thing in the morning: today I shall meet people who are meddling, ungrateful, aggressive, treacherous, malicious, unsocial. All this has afflicted them through their ignorance of true good and evil. But I have seen that the nature of good is what is right, and the nature of evil what is wrong; and have reflected that the nature of the offender himself is akin to my own – not a kinship of blood or seed, but a sharing in the same mind, the same fragment of divinity. Therefore I cannot be harmed by any of them, as none will infect me with their wrong. Nor can I be angry with my kinsmen or hate him. We were born for cooperation, like feet, like hands, like eyelids, like the rows of upper and lower teeth. So to work in opposition to one another is against nature: anger or rejection is opposition.

p12 Meditations by Marcus Aurelius