I don't think a story can be perfect, but I struggle (partly from inexperience and partly from personality) with knowing when it's good enough to stop touching.
I had a short story published last year that, after I gave it the last round of edits and submitted it to a few places, I started to feel I had
overedited - like overworked dough, there were places where my efforts to improve the shape of sentences had made them stiffen up. If the piece had not been accepted, I would have reverted to the second-to-last draft, at least partially, before sending it out again.
On the other hand, it
was accepted, so at least one editor thought it was just fine as it was, overworked and all.
Now I have a piece that's been rejected from about half a dozen journals, is still pending with a few more; and finished in the top 3 in one very respectable journal's annual contest. And now I'm wondering whether I should tweak it some more before I send it out again. After all, there are a couple of spots where I think it could be better, even if I'm not yet exactly sure how to execute. Maybe I should sit down with it and take another stab at those one or two passages that bug me (that I'd already rewritten several times before submitting in the first place).
I'm still not sure what I'll do. On the one hand, it placed in that contest! It must be pretty good. On the other hand, it didn't win the contest. Am I doing myself a disservice by not trying to make it better? Or is that energy better spent working on the next story? I don't know the answer.