In whatever you choose to do. Do it because it's hard not cause it's easy. Math and Physics and Astrophysics are hard. For every thing you accomplish fewer people are out there doing the same thing as you. That's what doing something hard means, and in the limits of this. Everyone beats a path to your door because you're the only one around who understands the impossible concept or who solves the unsolvable problem.
Neil DeGrasse Tyson