If you are at all like me you spend a significant amount of time beating yourself up for NOT doing what you know you should do.
Most of the achievement oriented people I know do this quite a bit. It is as though they are on a quest for perfection and anything less than that is unsatisfying.
Don't get me wrong ... I think it's a great thing to be on a quest for perfection, and I believe people who are, will ultimately experience a good deal of success because they'll never feel as though they've arrived. There will always be something else to accomplish.