This has bugged me for a long time, since I was an undergrad. What is the best strategy when doing challenging problems sets? And, what strategy do professors think you are using? When doing problem sets by myself, I will invariably get stuck on one or more of the problems. Now, I am not opposed to spending 5+ hours on a single problem. But it gets to the point where you have to cut your losses. Just put down whatever your best guess is and move on to the next assignment (because there is a never ending queue of assignments waiting). It seems like my classmates never have to do this. I think one thing that helps them is they have more collaboration. I try to collaborate with my classmates, but I am a little antisocial. I am not a prototypical nerd and I just don't mesh well with them. I go to office hours with my problems, but most of the time the TA is not willing to give me enough help to really get me going, unless I really have it worked down to a very specific question. What is the normal thing to do when you are stuck on difficult graduate level physics problems?