As for the idea of sin: I never got the impression we were meant to obsess over our own sins to the point of grief. Rather, I got the impression that we are to acknowledge our sins and try to overcome them. But if we can't, don't fret it! We're human after all. The fact that a person is aware of his sins already puts that person in a league far ahead of the person who is reckless and careless towards himself and those around him.