How does anyone know what happens when we die?

Nobody knows what happens when you die. Personally, although it would be nice to have a heaven of some sort, I haven't seen any evidence for it, so I'm not going to waste this life uming I'll get another. I think there would be a lot fewer wars and murders in this world if people realized that this might be the only chance at a life that they get - maybe they wouldn't be so quick to take away someone else's only shot at life.