For myself, sometimes when I finish writing something I’m like “oh my god finally, I don’t even like this story anymore!” which isn’t really true and it’s just me having a little fit to myself haha. And that’s usually the cue to take a break and come back later. For me at least, I dread going over first drafts because I’m kinda cringing at myself, but I’d be mortified to show it to anyone without AT LEAST doing a grammar or spell check

Over all I recommend giving yourself a second to breathe and maybe even read other stuff before you go back to it. When you have more distance from the person you were when you finished the first draft (not like, weeks or months, just maybe a day or two). What also helps us to write something between then, or it does for me at least. Not like a whole new draft but maybe some flash fiction or free verse poetry or even just an entirely different thing, like doodling. And it kinda gets me in the mindset of “this is not my baby, this is someone else’s baby. And I’m gonna drop the baby on its head”

I don’t know if this makes sense. Good luck!