Merlin Mann made this great observation on the most recent episode. I could certainty stand to get better at this; most of us could.
If it makes you feel better to beat up yourself, and you become more productive because of that, enjoy the five or six years you have left to live.
But otherwise, knock it off. I have to remind myself five times a day; the time I spend feeling bad about what I’m not doing is not being used to create anything. It’s being destructive not creative.