Well I think it is best to live your life as if you do wake up into the next life and have to be accountable for everything you thought said and did. If there is no afterlife then of course it doesn’t matter. But if there is..... a comfortable and happy eternity is nothing to sneeze at.
I think what we do matters, but empirically and in this world. It is sad to think the only thing that keeps some people from barbaric behavior is fear of afterlife punishment, but if that’s what it takes, I won’t complain. :)