Don't take that promotion if you aren't going to be happy. The problem with promotions is that they end up getting you into a new job. It's great if it's the work you're best suited for. And it might not be a great move if the work you are doing right now is the work you're most suited for.
The biblical author Paul wrote a lot about the nature of our skills and motivations (gifts given us by God). We were created with a certain set of gifts. And when we use them and work in areas that exercise those skills, we excel.
Pursue something you're good at or something you like. A lot of times they are the same thing. You will make a greater contribution to the world doing what you were meant to do, promotion or not.
For more on this watch the movie Happy Feet.
Or listen to this interview with Seth Godin.