I cannot stress this enough, write it poorly. Write the shittiest draft you possibly can, stick 'ah fuck something happens here and now they're fighting' to get over
Write the worst fucking version you possibly can and stick it in a folder and forget it for a month or two before you look at it again. You know what you have now?
A first draft. And with enough time to think some new thoughts about it, you'll soon end up with a better, second draft! And eventually, you'll end up with something you'd be perfectly okay with letting other people read!
You'll never believe this process works no matter how many times you do it, but it totally does. You just have to drag your brain kicking and screaming to that blank page and get the bones down first.
Write the shit out of that shit.
A shitty idea you can edit into something better is greater than nothing!