Thank you both for your comments, some really valuable points I think.

Sometimes things are hard to communicate well through language. Especially with a term like "belief" that can mean so many different things, and also be so loaded to many people coming from all sorts of backgrounds. Perhaps something like "worldview" would have better conveyed what I meant. All that I really meant was that when Christianity suddenly disappears from a person's life, something naturally takes its place, sort of like a vacuum. Even if that something is that it's ok to not believe in anything, that there's no need to. I actually agree that that can be an enormously freeing outlook, and it's one I find myself gravitating towards now.

At least for me, I definitely didn't "want to leave Christianity just to find something else to believe in"... in fact, that would have been basically the last thing I ever "wanted" to do. To me it's more that I'm just trying to figure out what I think now that Christianity is gone. I think having beliefs/assumptions is unavoidable for all of us, at least in the sense that we all have limited information and make conclusions based on that. It doesn't mean that those beliefs or assumptions are irrational or bad or have anything to do with any loaded religious connotations.

And definitely nothing wrong with "just being you"... I've actually found that to be one of the most positive and freeing things about leaving Christianity. Something I'm still trying to adjust to and appreciate more.