I am an atheist and do not believe in any afterlife, though the two aren't necessarily related.
Whilst the concept of us all being here for a reason is quaint, apart from religion, i don't think any body or belief system supports this to my knowledge, I'm probably wrong though, and would probably be just another take on the good going to heaven and the bad going to hell.
I'm far happier not even entertaining such a concept, I live my life not worrying about such things.