What shall I do??

I thought about my future in school library, yesterday.
When I think about my interesting field of study, I found that
I'm interested in many areas.
Since I was young, I used to think about scientist who study about biology.
But nowadays, I often consider about hair designer, accountant, musician,
dancer, professor and so on.
What shall I do when I am over 30 years old?
Actually, I really fascinated with music.