Before my recent vacation I tried a technique of "cycling through" all 8 chapters of my book, looking at them and revising them /adding to them one by one. I could spend as much or as little time as I wanted on each chapter during any given day. I wanted to get all the project into my head at once before not thinking about it all for a while. Whether I was able to write very many words on any single chapter was secondary.
Normally, it isn't good to scatter and fragment one's attention like this.