Fail.
I'm not kidding. Set out to fail.
This space intentionally left crappy | Mind-Manual
Cure you of your fear of failure. If you don't manage to fail, you fail at failing.
Also, perhaps your problem is that you have set too much time for work. For a week or two, give yourself the bare minimum of time. You're not gonna get more done in more time anyway, so test it out for another week.