Agreed. Been asked that before too. I have asked people like that why they think unbelievers have no purpose and why belief in an afterlife is necessary for anything to have meaning in this one, but never got a good answer to either. Possibly because it illustrated that they were never really sure what they meant by 'purpose' in the first place.

I don't know if the person who asked you was christian, Ephant, but if I assume they are then how ironic it is that they should ask at all. Judaism originally taught that one would get their rewards in this life, before getting wasted by the Chaldeans, and only afterwards started preaching that the rewards would happen in the afterlife. So the religion the Xians ripped off didn't even think like that at first. I wonder how all those deeply devout Jews got through the day with their meaningless lives that weren't going anywhere after death, but history shows they managed it somehow :)

Afterlife or no afterlife, those who believe and those who don't would probably still agree that life is generally what you make it and you are defined by how you live it. My life, and living it, is meaningful to me, I don't see the need to die in order to have purpose in my existence. I don't see why I have any less purpose in my life just because I don't live the whole of it for someone else, either. If purpose=meaningful then that is the purpose of my life, to live it and do everything I can. It may not be much of a purpose, it may not be a higher purpose, it may not be meaningful to anyone else but it's mine, I didn't steal it from anyone.

You only get one life but you can pick up a dozen causes on any street corner. The purpose of any of them is as subjective as any other 'purpose'. Who are you living for?
"All governments suffer a recurring problem - power attracts pathological personalities. It is not power that corrupts, but that power is a magnet to the corruptible" - Dune, Missionaria Protectiva.