I'm a PhD student in theoretical physics, and I am just amazed by how much physicists working in my field actually know. I am currently studying QFT and plan on going a bit deeper into General Relativity afterwards, but look at people like Rovelli or Susskind (just two names that came to my mind). I mean they know QFT , Statistical Physics, General Relativity, LOTS of mathemathics, and they mix up concepts in all of them, looking like they are at ease with everything they do. My question is....when the heck did they manage to find the time to cover that amount of material? I mean QFT (with Chromodynamics and GSW) , studied thoroughly, should take you at least a year...if not more. And GR takes about as much, if you go beyond the introductory stuff... Am I ok to feel like I have a hell of a lot to learn, even as a 1st year PhD student?