Sometimes the breakthrough is realizing you were solving the wrong problem well.

You can do excellent work for months and still end up nowhere, because the question you were answering was not the one that mattered. This is more common than doing bad work, and much harder to detect, since all the usual signals of competence are present. The moment of realising it stings and is genuinely the breakthrough, because it puts the same skill onto ground where it counts.

Every so often, step back and ask what would actually change if you succeeded completely at what you are doing. If the honest answer is not much, that is worth knowing now rather than at the end. Redirecting good work is far cheaper than continuing it.