"But what if it sucks and I hate it" then it sucks, nbd. It might also work out. you won't know until you try. Just keep a copy of your manuscript pre-changes so you can go back if you need to, it's fine.
"But I'm scared" Fear is the killer of creativity. Even if you can't turn off the fear, do it scared. As with point one, you can always just go back to a previous document or stop writing for a bit if it sucks or doesn't work out.
"But I'm on [draft no. # / revisions / edits] and I shouldn't be making big changes now" says who? sure, there are suggested goals for drafts and rounds of edits so you don't edit forever, but it's only a suggestion & you should discard it if it's not helpful.
"But it's so much effort" writing stories is effort. You've already put so much work in and it'd be a shame to ditch an idea for fear of doing more.
"It'll take so much time" it probably will. But, 1) as a wise person on the internet said, the time will pass anyway. 2) wouldn't you rather pass that time trying something new, instead of repeatedly banging your head against a story you're struggling to write.
"All of this is true but I feel [sick / miserable / exhausted / insert other negative emotion here] about doing anything with my story" okay then maybe it's time to shelve that project. That's completely fine too. Maybe your brain needs some breathing room or maybe the story as a whole isn't working and you need to start fresh on something else entirely (you've got plenty of time to figure out which). This doesn't make you less of a writer and it doesn't mean whatever you were writing was shit. And even if it was shit, like, who cares? We all have to write shit at some point. It's important. And now you can grow and learn and try again, because that's how you get better, and anything particularly cool in that story will eventually pop up in another project where it fits better (and often where you least expect it).
