Writer's schizophrenia

I don't know whether I've mentioned this in another post, but today I was forcibly reminded that writing(and rewriting) can be a "schizophrenic" experience. I'm rewriting Chapter 2 of The Invaders, the first book in my Great Medieval Science Fiction Masterpiece With Neandertals. The second chapter flows from the first, as it should. But there is so much of it! I simply cannot believe how much I wrote, that didn't need to be there. So, in revising --- for critiquem and, I hope, eventual publication --- I cut out about 1/3 of the beginning of the original first chapter. I also added a character that comes in later in the book, but wasn't there before, and dropped another one, that was there, but never really "jelled". This character, though minor, makes more sense, in the context. As usual, this is an interesting experience, to say the least. And I am taking quite seriously, the advice I'm hearing from other writers. If you're by yourself, and no one else is looking at your work, editing and re-editing, and smoothing out, is a daunting chore. I don't know how some writers do it. My worst faults are a tendency toward "passive voice" and a pace that's a little slow. I'm working on that, though.
Anne G