If anything, just force yourself to write even when if you're spewing out crap. Once you've got all your crap spilled out, you can revise and rebuild your shit piece by piece until it suddenly doesn't look like turd.
But don't worry; we'll still roast the shit out of you if you're a bad writer. That way, you can go back and fix it again and get better.
Repeat this anywhere from 5-20 times and you should come out with a work that would surprise the person you are today.