One of the pieces of advice you get while doing NaNo is never to revise while writing. If you think of something you need to change earlier on than where you're at, pretend that you did and move on. After all, your rough draft is going to be a complete mess anyway. I'm doing that.
I think I like this approach. It's making me think of other things that need changed earlier on. And it kind of has me thinking that outlining a book chronologically but backwards might be a worthwhile thing to look at.
Yesterday, I wrote very little (like 700 words) but I figured out a lot. It can be hard time quantify time spent working while writing. It's not just about word count. It's also not just about time spent. So far today I've written my daily quota, but I think I'm going to work some more.