Woodworkers say the project’s done when you’d rather use it than fix it. That’s a decent rule for everything.

Done is not a state of perfection, it is a change in your relationship to the thing. There is always another adjustment available, so waiting for nothing left to improve means waiting forever. The useful signal is when fixing starts to feel like avoidance and using starts to feel like the point.

Look at whatever you have been fiddling with and ask whether you would rather use it or keep adjusting it. If the answer is use it, stop now and call it finished. Put it into the world as it is, and let the next version take the improvements you were about to make.