Writing a book is a demanding task. I usually have problems in concentrating on the subject and not on the layout and visual appearance. But slowly I have improved, thanks to LaTeX. You don't have to worry about the finished book until it is finished. Do your planning well, be prepared to change the whole structure of the book, and use good tools. Writing is of course still difficult and poses problems, but that is in the nature of writing. Writing is one of the hardest things people do.