Probably to make the world a better place. I don't know how I'm gonna do that, But I hope somehow I would at least somewhat change it for the best. The new motto I've developed is "If you're not making the world a better place then why the hell are you still alive?"
As for afterlife, being non-religious and yet still being afraid of nothingness, I'd like to believe in reincarnation, as in you are reborn without knowing anything of your previous consciousness. Other than that I really don't like thinking about it.