What your hated trope, you used in your story.
A trope I hate that I used anyways...
I regret adding an antagonistic force to my story. My main conflict was supposed to be internal, but I was worried that nobody would be interested if I didn't have some world ending threat trying to eat my characters.
(Well, that's not the whole truth. I sort of reused old assets from older works of mine, and it was very convenient and reasonable.)
But when I finished with the conflict I set out to write, I still had this nasty world ending threat sitting around, and despite that, my heart said the goal was finished and I didn't need to write anymore. Trying to continue was like writing the sequel that nobody wanted.
I probably still could have finished it if life hadn't done its thing, but... Well, if I'd known how things would turn out, that's what I would have changed.