Without you, something will be missing. What I'm saying is that you are not here for any particular purpose. You are free to decide whatever you want to do. Trying to fit into some given purpose might prevent you from discovering your ultimate potentials. Almost any day, you can read about someone who has fallen over the edge and has chosen to bite the big one.
Insanity is a relative term.
Being a misfit is not a sure sign of being crazy, but most likely a sign of intelligence. I don't fit in myself. I don't consider the businessman who dashes off for work in the wee hours of the morning, is tense all day, fights traffic all the way home, eats dinner, has a few drinks and hits the sack, to be truly sane. There are many people who love their jobs, I'm not talking about them. It isn't what you do that matters, but the creativity and joy you bring to it.