Choose what I love to do


I have hard time to choose what I love to do as a career. When I grew up, I always did what I am being told to do. So I studied engineering in the college. However, I do not like what I do as a career at this point. Is there any tool I can use to decide what I love to? Also people are saying once you start doing something you enjoy doing as a career, you will loose passion eventually. Is this true?

Thank you,

Chao Sun