A passage from Epictetus
Epictetus, Enchiridion 50
✱
Whatever moral rules you have deliberately proposed to yourself, abide by them as they were laws, and as if you would be guilty of impiety by violating any of them.
Related passages
✱
At dawn, when you have trouble getting out of bed, tell yourself: 'I have to go to work — as a human being.'
✱
Take care not to be Caesarified, or dyed with purple; for it does happen. Keep thyself then simple, good, pure, serious, free from affectation.
✱
It is a man's special privilege to love even those who wrong him.