During my High School years, I've had great teachers who have inspired me. I will always remember my English teacher's famous quote: "Do it, not because you HAVE TO, but because you WANT TO!". She said that every time she was about to give us homework! (I repeated in my head: "I want to do my homework because I want to learn!")
Come to think of it now, whatever we do, we should do it with passion! Saint Augustine said it clearly, "Love, and do what you like." I guess it's the only way to move forward, and have a purpose in life, if you haven't found one yet. Some are lucky enough to have found their passion. As a funny joke, they'd rather pay, rather than getting paid, to do what they like. They are heads over heal in their activities, whatever that may be. They do not count the hours spent, they do not count their failures, they are rejoiced at the successes... although sometimes they may neglect their own health.
I guess the best way to find what you like is to try out different things, and try to think out of the box.