When I'm editing, I'm bad for keeping a million different copies of my chapters. Okay, maybe not quite a million, but a lot more than I care to admit.
I find that every time I go into the chapter I save it as a different name just in case I change something and then decide I want to go back to what I had previously written. And, of course, because I'm getting older, I can never remember the exact wording.
Hence I have a lot of the same chapter with just a few changes, which can be hard when you're trying to figure out what document is the most up to date. So with this book I've been using dates in the name, which so far is working well.
What about you? Do you save your chapter each time you open it or do you just rewrite and forget about what was once written?