Raymond Carver, a writer I love and respect, also enjoyed tinkering. He wrote, about another writer, that “he knew he was finished with a short story when he found himself going through it and taking out commas and then going through the story again and putting commas back in the same places.” I know that feeling exactly, for I have had the same experience many times. You reach the limit. If you tinker any more you will only damage what you have written. It’s a subtle point, easy to miss. The bit about replacing commas hits it right on the head.
