The result that works only under perfect conditions is not finished learning from reality.

A thing that succeeds when nothing goes wrong has only been tested against the easiest version of the world. Real use brings tired people, missing pieces, bad weather, interruptions, and wrong assumptions, and any one of those can undo work that looked complete. Fragility tends to stay hidden until the day it matters most.

Take whatever you are calling done and run it under one realistic annoyance: the rushed version, the tired version, the one where a key piece is missing. Watch where it bends. Fix that before you fix anything cosmetic.