Part of it may be fear of being found out. Part of it may be guilt if one chooses what is self-serving and selfish rather than what is not. I don't know how much of each it is but if you know you're doing something WRONG don't you always worry about being found out? For the rest of your life? Who wants to live like that? Always looking over your shoulder to see what is gaining on you. Plus which that's how you stumble because you aren't watching where you're going because you keep looking at where you've been! :(