How do I get past the fear that my writing isn't good enough?

The blank page is not asking you to be good. It is only asking you to begin. The fear that you are not good enough is loud, but it is not a judge. It is just the part of you that wants this to matter, turned against you. You do not have to earn anyone's attention before you write. That comes later, if it comes at all. Right now the only task is to get one true sentence down, then another. Bad first drafts are how every real writer starts. The polish is a separate job for a separate day. Set a small timer, ten minutes, and write badly on purpose. Give yourself permission to be clumsy. You are not trying to impress anyone in that window. You are just proving to yourself that the page cannot stop you. Do that a few days in a row and the fear gets quieter.