I wish I had a solution, but here are a few things that might help:

• Always remember that perfectionism is self-defeating.
• Try to do whatever you're trying to become good at (writing, drawing, music, etc.) for a long time. For example, if you've only ever written two blog posts, you might feel quite perfectionistic about the third one. But once you've written 1000, you can't help but care less about number 1001.
• Try to find an activity you don't feel perfectionistic about and do it regularly. Successes in that area will then show you that it's not perfectionism that gets you somewhere. For instance, I have perfectionist tendencies with my writing, but not with my comics. So doing comics and seeing that they are popular despite not being perfect has helped me be less perfectionistic about my writing too.