Here you go ISF. Not quite a one-liner to live by but I think this is something you'll enjoy.

http://www.sfgoth.com/~immanis/rilke/letter1.html

A young poet sent his works to Ranier Rilke looking for criticism, encouragement and whatever else. Rilke sent him back these letters. They are full of great quotes.

"If your everyday life seems poor, don't blame it; blame yourself; admit to yourself that you are not enough of a poet to call forth its riches"