@mjb I can relate:

Pirsig’s descriptions of the hard-won self-discipline (and exhaustion) that the writer’s life requires will ring true for anyone who has tried to write a book. He sums up his motivation succinctly: “this was really a compulsive book. If I didn’t do it, I’d feel worse than if I did do it.”

http://www.openculture.com/2017/04/robert-pirsig-reveals-the-personal-journey-that-led-him-to-write-his-counterculture-classic-zen-and-the-art-of-motorcycle-maintenance-1974.html