What should I be when I grow up....

I have been trying to figure out for some time now what type of career or life path I should take. I want to wake up in the morning and be excited about what my day might bring. I have no idea where to start. I have been told to look at my hobbies and passions and decide on a career that encompasses them, but the trouble is I don't have much for a hobby or a passion. I've thought about aptitude testing, but I'm not sure I would get the right the answers. Hmmmmm..... any suggestions??? Where to start? How to decide?