I stole this advice from somewhere, I don’t even remember where I first heard it. The advice is Do Your Worst.
I’ve tried it a number of times and it’s strangely liberating. You fear you might suck? Find out. Write to suck. Go out of your way to write the worst sort of writing you can think of. Do everything “wrong”. Going through the worst will make it seem less worrisome.
Chances are, deliberately trying to be bad will result in something pretty good anyway.