How do I know when my work is good enough to stop?

You keep refining long after anyone would notice the difference — the tenth revision, the invisible tweak. The trouble is you cannot feel when a thing is done, so you keep pouring hours into improvements that only improve it for you. The polishing has stopped serving the work and started serving something in you. Usually that something is the discomfort of letting go. As long as you are still working on it, it is not yet up for judgment. Perfect is not a real place you can arrive at; it is a horizon that keeps moving. Chasing it is a way of never having to call the work finished and face what people think. Give yourself a rule: define what done looks like before you start, then stop when you hit it, not when you run out of energy. Or set a timer for the polishing and let it end when the timer does. Practice finishing on purpose. The relief of shipping is a skill, and it grows each time you use it.