Reading this section of Anne Lamott's book brought to mind many of the times I've struggled and found myself backed into a corner when writing a boot. So many times I've done what she did and went back to the beginning to figure where I went wrong. She speaks of the book she'd worked on for two years and had her editor say it didn't work. I imagine the way she felt. After reading Bird By Bird for the first time, I began something that has worked for me.
The rough draft may wander all over the place and much of it won't be in the final version. No one sees this but me. Why? Frankly it doesn't make sense. Once I have the rough draft out of the way, I sit down like she did and do a treatment for each chapter of the book. Usually not more than a paragraph or two. Now some of these change as the story evolves, but having a plan is better than spending weeks and days on writing something that's not going anywhere. Whether it's flawed characters which hopefully you've made part of your psyche. Writing is something like acting. You need to become the characters you write. A flawed plot. Deciding where the important segments should be placed and you won't end up writing a book that wraps up the entire journey in a page or two.
Try a story treatment. Look at each chapter and find the purpose of that segment. Are you developing the characters, advancing the plot or giving needful information. If you can do more than one in a scene congratulate yourself and if all three figure in, you should have a scene that makes the story and the characters live.