EV, what do you mean by compulsive sin? Are you talking about OCD? Most people with OCD tend to be overly conscientious and to go out of their way to avoid sin or any harm to anyone, although they worry constantly that they are doing something bad and have to atone for it. So, they might feel like they are sinning when really they aren't. I don't know what kind of sin you are talking about though, or if what I wrote is close to what you mean.

I believe that God will always take into consideration our ability, and that He is loving and understanding. He also knows what we are capable of and isn't going to put us in situations that we can't find our way through. He does expect us to do what we can, and then He will help us and make up the difference. So we do have a responsibility to break bad habits and improve ourselves as much as we can.