Instead of thinking you failed - put it in a different light. You will complete some or all of the challenges. You will have a good idea of the book whether you finish them or not, and if it carries over to when time is less intense - so be it. You'll still have the idea, a bunch of work toward the prep, and you work ahead so that book will still be there. YOU GOT THIS! It's the seed of a book that might not be finished, but you have time.