The bug that took three days to fix taught you more than the code that worked on the first try.

Things that work immediately teach you nothing, because you never find out why they worked. Three days of being stuck forces you through every assumption you had, and what you are left with is not just a fix but a map of the territory. The frustration is the tuition and the understanding is what you bought.

Keep a short record of what actually cost you time and what it turned out to be. When something breaks, resist trying random changes and instead write down what you believe is true before you test it. The slow repair is where the real knowledge gets made.