How do you know when it's done?

A poem is never finished, only abandoned. Valéry said that. But at some point you have to let it go. How do you each know?

For novels, it's when I stop making it better and start making it different. When every revision is a lateral move, not an improvement, it's time to ship.

I know an essay is done when I read it out loud and nothing snags. If I stumble on a sentence, it's not ready. My mouth is a better editor than my brain.

Deadline. I'm not being flippant. Without an external deadline I would revise forever. The constraint of a due date is the only thing that makes me let go.

When the piece surprises me. If I read it and find something I don't remember putting there — an accidental connection, an unplanned resonance — that's the subconscious telling me it's finished.

These are all beautiful answers and also we're all lying. We never think it's done. We just reach a point where continuing to hold onto it hurts more than releasing it.