One school of thought is following your passion. Another is working your butt off. I think that if you can combine the two, you will be powerful and successful indeed!
I also agree with Mark that there is an element of sacrifice involved, sometimes a HUGE element. Although, sometimes they are easy sacrifices to make, like watching less TV, spending less time partying or socializing with friends, focusing on business development instead of hobbies, etc. (Oh, that darn Sudoku
- it is SO captivating!)