Originally Posted by songwriter
Your purpose should be something that the best thing you could do to make the world a better place or so...
What makes me "come alive" is music... but not when I share it with people (performance, they listening to my songs) but only when I play, sing or compose in my home.
Is my purpose related with music then?
I would guess it's in that field somehow. As someone who's aced tests or made significant life changes on the basis of having the right song in my head at the right time, I would be honored if I could create a piece of music that changed someone's life the way some music has changed mine. So I don't see any reason that you couldn't have a very worthwhile purpose in that area.
As to what that specific purpose is... only you can answer that.