To use a very illustrative lyric: "I only accept critique from those who are trying to lift me up". That includes you.
It takes practice but especially for your first draft, you really just need to word vomit onto the page so you have something to work with. It's gonna be shit, repetitious, muddled metaphors, bad grammar... It just needs to get out like poison. Working on saying "yeah it's bad but for now that's the point, I'm doing it right" and pushing through without listening to the bagging voice saying "but it's bad though" took a bit of brute forcing in my case. I hate first drafting for that reason. Currently doing it now for a horror anthology, awful.
Then on the second draft you only accept comments from yourself that are useful for improving the prose.
"This word choice needs to change, it doesn't work" "This scene isn't serving a purpose, I should delete/merge it" "This character is falling flat, i need to rewrite them" "this metaphor isn't saying what I need it to say" "I need to restructure this whole story because I now have a clearer view of what I want this to be so draft 2 is going to look very different from draft 1", etc...
"This is shit" "no one will want to read this" "people will laugh at me" "this is useless" "I can't make it as good as X story i love" etc...
You kind of have to Pavlov yourself, everytime you start te get paralysed by an unhelpful thought (and to be clear, some helpful thoughts are unpleasant, so it takes a while to distinguish the two), you have to stop and tell it no, it's wrong, and dismiss it.
You have a story to tell and something inside you made you want to start writing it, so remember that something. You were compelled to put pen to paper, and you can do it. Take your time, breathe, and work through it. 