A finished project can be a source of pride even when you already see how to improve it.

Seeing the flaws is evidence that the work taught you something rather than evidence that it failed. Whoever you are at the end of a project knows more than whoever started it, which is exactly why the weak spots are now visible to you and were not visible then. Pride and improvement are not in competition.

Let the finished thing stand as it is. Write down what you would do differently, put it toward the next one, and stop reopening this one to prove the lesson.