*sigh* Faith has no grounds. It's just...faith. Believe! Believe in whatever your taught, or read, or want, or I say, or he/she says! Since you don't have proof, just believe!
I don't live my life based on things I don't know. In either case, I'm no less 'naive' than anyone living. None of us really know what's on the other side. And we won't until we get there. How we live this life is up to us, that's the beauty of life. We can live how we want.
I was LDS for 19 years of my life, straight from birth. I know the first thing about being heavy into religion, and the most involving religion in Christianity, at that. I know all about it, and the teachings, and not just of the LDS church. I 'believe' now that we should live life happy, not unhappy, especially since we don't know what's waiting (or not waiting) for us.