A passage from Marcus Aurelius
Marcus Aurelius, Meditations 3.11
✱
To the aids which have been mentioned let this one still be added: make for thyself a definition or description of the thing which is presented to thee, so as to see distinctly what kind of a thing it is in its substance.
Related passages
✱
Take away thy opinion, and then there is taken away the complaint, 'I have been harmed.' Take away the complaint, and the harm is taken away.
✱
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.