Serenity

"Grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference."
-  Reinhold Niebuhr ‘34

This is one of the greatest quotes and both a principle for effective actions as well as a sanity check on strategies.

Originally used as a prayer by Reinhold Niebuhr it encourages humbleness and at the same time has a challenge to not settle for less than what can be achieved.

Reinhold Niebuhr