I've been really struggling to stick to a single project lately. I keep jumping between different ones, I don't really know what to do. Also, any advice on vomit drafts. I've heard there good but I don't know much about them.
I can relate. I have a poor track record when it comes to sticking with a project. If we're talking short stories of 5K words or less, I can usually finish them before getting distracted by the next shiny thing, but anything bigger... I've got two massive, sprawling novel series going right now, and I've switched between them often, though lately I've been doing pretty okay at staying consistently with one of them.
I'm not sure that jumping around is necessarily, completely, a bad thing. I think it has its perks, though it's definitely something to keep an eye on if you're concerned about producing a finished story. Speaking from personal experience, having two huge projects gives me somewhere to go if I really get bogged down with one of them. If I work actively on Series A, there'll come a point when I get bored and frustrated with the whole thing and I just want out. While working on Series A, certain ideas for Series B will have manifested as I go about my days. Having left Series B alone for, say, 6 months, it'll feel reasonably fresh and exciting yet familiar when I get back to it, and I'll have all these juicy new ideas to implement.
I will say that this is not a method I recommend to anyone, it's simply what I've been doing. It's a tricky line to walk between letting a project cool off, and maintaining momentum. There really is no formula for this that I'm aware of, it's something you have to play by ear. It helps in my case that they're both Fantasy Comedies written in a similar style, taking place in the same universe with some crossover stuff. The swapping is part of how I find fun opportunities for Easter eggs and more involved crossovers. I think of these two series as part of the same overarching project, even though they're for the most part self-contained stories.
If I get sick of writing one story, going over to the other for a bit feels almost like vacation. It's good for spotting places where I repeat myself, like tackling a theme twice in more or less the same way or writing a too-similar character. I find places where one storyline or thematic inquiry from one story naturally sort of continues/branches off in the other.
I don't think any of this really addresses your question, I was just really in blather mode. As for how I stick to a project, the answer is I don't. Back in the day when I wrote only short stories I'd happily juggle up to five or more at a time, plus working on a novel besides, while working on an art piece and designing a board game on the side. I think the quality of all of them suffered. There is demonstrably such a thing as too much swapping. Nowadays I stick with my two novel series, with long cycles before a swap, with ordinarily no more than a single short story on the side and often not even that.
I think the thing is... One you've gotten really settled into a project, when you've got roots and emotional investment and actual passion about a project, it's okay to leave it aside for a bit to explore other things. Scratching the surface of a dozen different stories and never digging deep on any of them is probably largely a waste. As least it felt like one when I was doing that sort of thing.
I'm not familiar with the term "vomit drafts" but I suppose it explains itself. Not something I do or think would fit my workflow.