Or, more specifically: sex.
I mainly write on procrastination and perfectionism in one's work, but the same principles apply in other parts of our lives. Here's Andrew Sullivan nailing it (so to speak) relative to perfectionism in our sex lives:
"If your standard is never to commit a venial sin, you will almost certainly fail. And you may set up a destructive pattern of perfection, failure, depression, more failure, more depression, a new commitment to perfection, failure ... and so on: rinse and repeat. I think that cycle is horribly destructive and believe that moderation and risk-minimization is a safer guide to avoiding sin than total abstinence."