Must...Pass...

Gam zeh ya'avor.

Which is a Jewish proverb meaning "this too shall pass"...the story the proverb comes from is quite interesting, actually.  A great king, wishing to teach one of his courtiers a lesson, told him to find a thing that would cheer a sad man and make a happy man miserable.  After a year of searching, the courtier was returning through the royal city and stopped to bemoan his failure to a local tradesman.  The man, however, was not dismayed, and, taking a simple gold ring, scratched the above engraving.  The king, once presented with the saying, was humbled, for he realized that, just as hard times may pass, so too all his wealth and power was a transient thing.

Abraham Lincoln also used this maxim in one of his speeches.