Okay, so I revised Chapter Four again today, after having revised it yesterday, too. I'm feeling much better about it today than I was yesterday.
However, last night/early this morning I planned how I was going to revise Chapter Four and start Five. I don't believe any of it went into Chapter Four, and, in fact, some brand new previously unthought of material went into it this afternoon. What I had planned to be Chapter Five is now Chapter Six. Chapter Five is a chapter from an earlier draft with some brand new material at the beginning--material I only thought of this afternoon.
This is not the first time something like this has happened. Really, it makes me wonder why I try to plan at all.