This quote/proverb thing is kind of well known, but I like it a lot.
"One evening, a Cherokee elder told his grandson about the battle that goes on inside people's heads.
He said, 'My son, the battle is between the two wolves that live inside us all.
One is unhappiness. It is fear, worry, anger, jealousy, sorrow, self-pity, resentment, and inferiority. The other is happiness. It is joy, love, hope, serenity, kindness, generosity, truth, and compassion.'
The grandson though about it for a minute and then asked his grandfather, 'Which wolf wins?'
The old Cherokee simply replied:
'The one you feed.'"