Hello,
What motivates me? I want to see how the book will end. I have tried writing on all day benders, and find that I burn out and the quality of my work goes down. So, I limit myself to a given amount of time every day, stopping where I know I can pick up again the next day. Sometimes, I make a few notes, or jot down a few questions that I will want to deal with the next day - mostly to maintain a sense of continuity, and to make sure I don't let the various threads get too tangled.
Genevieve