How do i know what i want to be when i grow up?

im rite now 12 and ive been thinking about what i want to be when i graduate from high school. first i decided to become a lawyer. but then i found out that most of them have trouble being successful, so i dropped the idea. next i decided to become a screenwriter because i LOVE movies. i still want to become a screenwriter. but their wage is to "average-y", even though its something thats related to movies, which i LOVE (yeah, repetition!). is it worth become a screenwriter though?