A colleague recently forwarded these words to me, which are written in the Tao Te Ching and attributed to Lao Tzu:
Fill your cup to the brim
And it will spill.
Keep sharpening the knife
And will become blunt.
Chase after money and security
And your heart will never unclench.
Seek the approval of others
And you will become their prisoner.
Do your work, and then step back.
That is the only way to serenity.