I love Pema Chodron's little book called Taking the Leap. I've read it a couple times now, and don't see myself stopping at that. Here's my favourite excerpt, (which you may have encountered before):
"There was a story that was widely circulated a few days after the attacks of September 11, 2001, that illustrates our dilemma (speaking of the dilemma of living in today's world). A Native American grandfather was speaking to his grandson about violence and cruelty in the world and how it comes about. He said it was as if two wolves were fighting in his heart. One wolf was vengeful and angry, and the other wolf was understanding and kind. The young man asked his grandfather which wolf would win the fight in his heart. And the grandfather answered, "The one that wins will be the one I choose to feed."