Yes, mortality is terrifying, but here's a thought: If you honestly believe that there's a life after death, you may be tempted to waste your life with pointless stuff. If you manage to accept mortality for what it is, you realize that the time you get in this world is precious, and that other people's lives are precious. You use your time more wisely and live a fuller life. You also realize that murder is putting a very final end to someone's existence because they won't get any extra time after death. I would submit to you that this actually makes you a more moral person than someone who believes in the morals of the bible.