Life matters a lot less because you know you just need to do a few things to please God and you'll live forever in a paradise. If good people go to heaven after they die, why does it matter if they die? It's a part of God's plan, isn't it?
Well, it is a good point, but who said that every person who believes in afterlife gives up because of what you said? I believe in God/heaven, and I don't believe that I can just give up after doing a few things well.
Hey, why not bring proof? A testimonial will do, find me a few people who do what you say.