If we live long enough, we all find our limits. Learning to work within those limits and succeed in spite of them seems like one of the great leveling-ups of life.
John von Neumann springs to mind, who did his mathematics PhD at the same time as his chemical engineering degree, with a friend of his commenting that Evidently a Ph.D. thesis and examination did not constitute an appreciable effort. [0]
To my knowledge he never really failed at any of his intellectual pursuits, but I could be mistaken.
[0] https://en.wikipedia.org/wiki/John_von_Neumann#University_st...