Follow your interests and try not to become discouraged when things get difficult. Most worthwhile endeavors take work and perseverence. You won't know where you can end up unless you try.
I want to stay right where I am and doing just what I'm doing now: helping to further humanity's quest for knowledge.
The part of the mission that is most interesting to me is whatever I am working on. If I cannot get excited about what I'm doing, I won't accomplish anything that I can be proud of.