Realized that I had left threads hanging. Namely, what threads my heroine was bringing along to sew with. (Yes, it has plot significance.) The one real downside of being able to revise the earlier portion of a tale is that you have to remember to do it.
And was cantering along but having to stop and take notes. Plot holes!
This is why you need to revise quickly as well as slowly. To make sure you can keep it all in mind as well as you would when sitting down to read someone else's novel in a day. Even with a story as long as this one.