The Coen Bros were asked "How do you know when a script is done?" They answered "When we get bored with it." I understood immediately what they meant. If you can't fix it and you can't exploit the themes any further, it's done. Your eyes glaze and you want to simmer in a happy nap. I've yet to take a nap like that but I find a way to feel comfortable with a script long enough to produce it (see: my comix & plays), even if it has wiggle room to improve. And, that's what keeps it fresh and exciting for me. That wiggle room.
Earlier this year I had a great idea for a play. My gut knew what I wanted but when I started to explore and exploit the concept, it derailed. Became something else in the second act. I lost my idea and skidded into a direction that was not funny, morbidly verbose, and problematic. I realized I was appealing to some outside sensibilities (a perceived audience?) and wasn't honoring my own. I was faking the funk and it stank. What I wrote was more an essay, an apology to a toxic subject that has been occupying my mind for a few years. After one reading of it with a group of actors, a director & producer, I pushed the project aside. Buried it. Lost my confidence. I knew there was a good idea in my initial idea but I haven't cracked it yet.
Then something weird happened. I reacted to my new play with a NEWER play. It spilled out of me in a few weeks. I had become allergic to my previous play and reacted to it in a proactive way by writing what I should have written all along. Completely different in tone and story and characters but a better version of what I disliked in the abandoned play.
I'm all for pushing your boundaries and challenging yourself creatively but, knowing how to apply your skill set, knowing what you can and cannot do well is important. I spent the first 50-years of my life studying, learning, practicing and making mistakes. I'd like to believe I'm entering a phase where it's okay to lean into what I know, what I like, and what I'm good at. Rely on my earned instincts.
Make the stuff only you can make and let it roar like a thousand lions!