[throwaway1979]

As someone who can count the number of B's I've gotten in one hand (K-PhD), I have to relate a saying: "grades don't matter ... it's just how we keep score". In the original version of the saying, money comes in the place of grades :-p

But seriously speaking ... at some point, you will stop caring about grades. I stopped grading after I starting grading undergrads as a lecturer. Heh .. I stopped caring about my age after 31. As a former child prodigy, I sometimes do feel I've wasted opportunities and my potential. But then I remember that the battle isn't over yet ... I may yet do something I feel is consequential. It is no longer an achievement in science. Rather, I hope I can create a company that gives a livelihood to many people, treats them well, and does right by the world. Given that I don't even zero entrepreneurial experience at this point in my life, this dream might just wither away. But c'est la vie.