As long as the natural life is in your body, it will do a lot towards repairing that body. Cut it, and up to a point it will heal, as a dead body would not. A live body is not one that never gets hurt, but one that can to some extent repair itself. In the same way a Christian is not a man who never goes wrong, but a man who is enabled to repent and pick himself up and begin over again after each stumble….
The Christian thinks any good he does comes from the Christ-life inside him. He does not think God will love us because we are good, but that God will make us good because He loves us; just as the roof of a greenhouse does not attract the sun because it is bright, but becomes bright because the sun shines on it.
— C. S. Lewis, Mere Christianity, quoted in A Year with C. S. Lewis