Why this is a mistake: A book is a large investment of time and energy. Often over a year’s worth. Simply just typing 100,000 words takes a long time. Most writers don’t want to let go of that much work. I’ve watched writers come back year after year to the same writers conference with the same manuscript, reworked and edited, trying to sell it. Rewriting can only fix so much. It can change story, but it can’t change an idea.
If the core idea of the book simply isn’t strong enough to sell, it doesn’t matter how many rewrites the manuscript goes through; it just isn’t going to be the one to make it. Sometimes it just isn’t the right time no matter how good the book is.
The bigger problem with not letting go of early works is that you learn by writing. The next book you write is going to be better. But if you never move on, then you can’t get better.
The solution: There comes a time when you just have to put that manuscript in a drawer and let it go. Start writing a new book. Consider it an investment in learning. Most published authors I know did not sell their first manuscript. Many did not sell their second. It was around number three that they started seeing success. A rough rule of thumb? Give it a year. Beyond that, move on and write something new.