revising and rewriting

I have divided my novel into five segments of roughly 20,000 words each, and at this moment I am keeping only the first segment on my computer. The other sections are stored elsewhere. I am going through it scene by scene, and I’m sad to report that very few scenes are fine the way they are. I’m finding that certain scenes need to be partially or fully rewritten, while most others need some kind of alteration. Most of this alteration involves deeping the characters and providing a little more backstory on them in order to shed light on current motives and increase reader interest. Anyway, I think (I hope!) this process will go more quickly as I progress through the sections of the book.