Fallen man is not simply an imperfect creature who needs improvement: he is a rebel who must lay down his arms…This process of surrender–this movement full speed astern–is what Christians call repentance. Now repentance is no fun at all. It is something much harder than merely eating humble pie. It means unlearning all the self-conceit and self-will that we have been training ourselves into for thousands of years. It is killing part of yourself, undergoing a kind of death. In fact, it needs a good man to repent. And here comes the catch. Only a bad person needs to repent: only a good person can repent perfectly. The worse you are the more you need it and the less you can do it. The only person who could do it perfectly would be a perfect person–and he would not need it.
–C.S. Lewis, Mere Christianity
according to Script 