And some more from Marcus Aurelius' Meditations:
"Never allow yourself to be swept off your feet: when an impulse stirs, see first that it will meet the claims of justice; when an impression forms, assure yourself first of its certainty."
"Do not copy the opinions of the arrogant, or let them dictate your own, but look at things in their true light."
" Observe how all things are continually being born of change; teach yourself to see that Nature's highest happiness lies in changing the things that are, and forming new things after their kind. Whatever is, is in some sense the seed of what is to emerge from it. Nothing can become a philosopher less than to imagine that seed can only be something that is planted in the earth or the womb."
"Observe carefully what guides the actions of the wise and what they shun or seek."