moving on to a new project

I wonder if you're not mentally done with the previous novel enough to move on to the next? I don't mean that as an insult, but as an indication that you might have some unfinished business with the old one.

This happens to me, so I totally get it. Either I need to work on the earlier novel to move it along in the revisions, or to leave it alone for a while longer so my mind changes gears to the next one.

I'd move on to a next story whenever there's inspiration for it. So, yes, it happens that there is more than one person "talking" in my head But when you think about it, people are not all radially different from one another either and if characters happen to be a bit samey, that doesn't trouble me either.

Often I do something different in between working on projects to cleanse the mental palate. In the case of novels, like yours, I would take a little time and maybe read or watch TV in a different genre.

I do the same thing when I have to edit project A and write for project B in the same day. Giving my mind something very different to do between working on the two can help reset everything. Though, YMMV.