I found a lovely summary of the typical reasons Ph.D. students struggle and fail. Well worth reading over for inspiration and reflection.
My favorite part: “A Ph.D. is not the final undertaking. It’s the start of a scientific career. A Ph.D. does not have to cure cancer or enable cold fusion. At best a handful of chemists remember what Einstein’s Ph.D. was in. Einstein’s Ph.D. dissertation was a principled calculation meant to estimate Avogadro’s number. He got it wrong. By a factor of 3.
He still got a Ph.D. “