I've always been the sort of writer who has a one-track mind. Once I commit to a project, that's it. That's what I'm working on, and I'm working on it until I'm done. But lately, it hasn't been like that. I've recently found myself working on two different books at once, and I'm weirdly synced up because they're both on the same chapter right now. Have you ever been undecided while writing your books?
One Way or Another
Focusing on a single story has always been my habit. I think about it when I'm not writing it, I worry over it when I don't really need to, I go back and reread it way too many times. But I realized, after a particularly poignant moment, that I have a habit of getting way too involved. And that's not good for me.
Up to a certain point, every author has to remain somewhat detached from every story and every character. Every author has to be this way, because almost every author ends up becoming a murderer -- of literary characters, that is. So it doesn't really pay to get all involved with a certain character or a particular story. It never does, because eventually that story will come to an end. You have to move on, and if your heart breaks every time you're doing a lot of damage to yourself.
So maybe working on multiple book projects is actually better than a single-minded pursuit. Working on two stories makes it easier to stay detached from both of them, because you always have another to think about. But if you're going to work on two manuscripts at once, outline them both clearly. Have complete character lists and notes, and keep these two projects in distinctly separate folders.
Stay undecided, and work on every project that strikes you -- just make sure you get something finished in a timely fashion.