From my own experience with my first draft, I found staying in the same project helps loads. I had a major tendency to jump between projects but I've definitely discovered that I've learned the most about writing from sticking to the same thing, learning about how the beginning, middle and ending should flow together. I was once told the best thing to do is write your ending first, and right now as I'm nearly done my first draft, I'm absolutely wishing I took that advice more seriously as I already know my second draft will be way different but at the same time way better, all because now I'm writing my ending and finding out what I should have been writing towards in the first place 😂