I found an answer to that, and it's made all the difference for me - I know why I'm doing what I'm doing, I know that my work makes a difference, and that makes the rest of this much easier. If I suddenly had $50M, I would still be working in the space I'm in.
Simultaneously, it's given me balance. I don't have the same frantic energy I had before - I'm doing meaningful work, I'm in this for the long haul, and I can't do this alone, so I can pace myself instead of panicking that I need to keep studying so I can reach my next career milestone.
The philosophers were right - find your meaning.