Introduction by Rick Warren "A handwritten note from Mother Teresa hangs on my office wall. It says, 'Be holy because the God who created you is holy and he loves you.' Mother Teresa didn't just believe those words; she incarnated them . . . By the time she wrote the note I've framed on my wall, leaders from around the world would listen to Mother Teresa. Why? I call it the Mother Teresa principle: The more you care about the powerless, the more power...