When is it Time to Let Go and Publish Your Novel?

You may have heard the phrase, “Better is the enemy of good.” Surprisingly, most people don’t actually know what this means. The phrase refers to the fact that it could always be better when you produce something good. You could. Therefore, spend an eternity making it better while never actually bringing it to market at all (whatever “it” is). In the case of your novel, yes, your book could be better… and the longer you take to finish it, the better you will get at writing, which will cause you to see things you want to change. Depending on how slowly you work, this could become a vicious cycle in which, by the time you’re done rewriting the book, you go back to the beginning and start rewriting it again.
We’ve all known authors (well, at least I have) who spend years writing and rewriting the Great American Novel, struggling to reach a point where they’re comfortable publishing. If you’re a perfectionist, nervous, or fear what will happen once your book is published and people actually start reading it, you could opt for the relative comfort and familiarity of repeatedly rewriting, editing, proofing, and rewriting a novel. Then, you’ll start showing it to friends, family, beta readers, proofers, etc., and you may spend years more rewriting and noodling around with it.
Only you can know when to call a halt to all this. If you’ve written it, gotten beta feedback, taken that feedback into consideration, made revisions, and had it edited, proofed, and proofed again, the book isn’t going to get so much better that it’s a different book. And yes, every book has the potential for typos, even after thorough proofing. Remember that every book you publish was as good as you were capable of making it at the time. Do your best with it… but once you’ve checked all those boxes, it’s time to get on with things.
Don’t give in to the urge to rewrite endlessly. Let it go once it’s good, and you’ve made every reasonable effort to improve it. Publish it and move on to the next project. See your projects as a way of getting iteratively better at the craft of writing; your new books should make you cringe when you look at your old books from years ago. That’s what it is to be a writer, and there isn’t a successful writer on the planet whose early work doesn’t seem less “good” than their later ones (as long as they kept working at their craft). Follow that example. Get ready, but then publish. The time to stop waiting may be now.
