He was kidding himself. He was in no shape to write night and day. His creative interest in the book had stalled, a recurring affliction that Mark Twain eventually came to understand metaphorically as his "tank" running dry. He also came to understand -- later-- how to deal with the "dry tank": put the manuscript aside and wait, for months or years, until the tank filled up again.
Some people have been asking what has happened to my blog; am I okay? I'm okay. My "tank" will fill up again when it fills up. I just hope it isn't months or years.