Why do I hold my work to a higher standard than needed?

You pour top effort into things that only asked for ordinary effort, and you know you are doing it, and still you cannot seem to stop. The standard runs on its own, disconnected from what the moment actually needs. That is not the same as caring about quality. Real quality includes knowing how much a thing deserves, and giving it that, no more. Effort is not free. Every extra hour you spend lifting a small task to a perfect finish is an hour taken from something else, or from rest. When the standard ignores what the situation requires, it stops being a virtue and starts being a leak. Matching your effort to the need is not laziness. It is judgement, and judgement is the higher skill. So practise doing something to exactly the level it calls for, and stopping there on purpose. Pick a low-stakes task, decide up front what good enough means, hit it, and walk away while you can still see improvements. It will feel wrong at first. Sit with that feeling. You are training the muscle that decides what deserves your best, so your best lands where it truly matters.