A Goodreads user
A Goodreads user asked Stuart Aken:

Hello Stuart, When do you know that a chapter/story is really finished being written?

Stuart Aken It's a movable feast, Emeline. You self-edit before sending work off to the publisher, reaching a stage where continuing to tweak no longer seems to enhance the story. The editor at the publisher's makes some other adjustments, almost always improving the piece. The book's published and you write something else, something different. But, later you revisit the original piece, the published work, and you see places where it could be improved.
This happens with all created work because the creator, the artist if you like, learns the trade, the craft over a lifetime. Most writers are their own most severe critics (beware any artist who claims to have produced something perfect!) so we will always find ways to improve our work as we mature and gain in experience.
There is, as you will now realise, no particular time when a piece of writing has reached the 'finished' stage. All we can do is recognise that, for the time being, the story is as good as we can make it, in the full knowledge that we will look back in a few years and identify faults and inadequacies. Such, I'm afraid, is the lot of the creative artist.
I hope that helps, though I suspect not. For your own work, the best I can advise is that you read it aloud as a final exercise, preferably from a printer script, not on screen. This 'final' check will reveal things you missed on screen and when reading silently. After these mistakes or failures of expression have been dealt with, send it off. As Wellington said, of a somewhat different issue, 'Publish and be damned!'
Good luck with your writing.

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