The photo at the top of this post is the map for a tavern I've designed for the Fate game I'm trying to write. I've drawn more than four draft versions of it, and then at least two "final" versions. It's from possibly the earliest planned-out scene in the game, and I'm totally fixated on it.
It's not even a plot-important location (at least, not yet). I'm not planning for there to be any combat in the place. The specific layout of the rooms is of no consequence. But I've redesigned and tweaked it several times.
This happened the last time I tried to run a game, too. I became obsessed with the details, including plenty of stuff that I'm pretty sure the players didn't even notice. To the point that I ended up railroading the adventure really badly; I quickly realised how badly it was developing and packed it in.
The root of this fixation is almost certainly a desperate attempt to retain control over the scenario. I've spent the last couple of years thinking of this story, and the last couple of weeks whipping it into an actual narrative.
The closer it gets to being ready to play, the more I'm realising that my directions for the story are going to be almost-instantly derailed by the players - through no fault of theirs. It's just the way these things go; unlike a videogame, tabletop RPGs support wild experimentation and unorthodox approaches, and having the arbiter in the room to argue with just encourages you to try something different.
Rolled into that with Fate is its idea of "collaborative storytelling" - how are you supposed to plan a long-term campaign if it's also got to support story threads and subplots from the players? I could try to direct the character creation into stuff that helps my established "canon", but that seems to be missing the point.
So I'm fixating on this tavern, telling myself I don't have to run the game until it's perfect. That way, my work can never be rendered obsolete by something as messy and unpredictable and fun as player choice.