Only a follower of Christ can know the assurance, the joy, that come with the promises of the Father. "Surely goodness and mercy shall follow me all the days of my life, and I will dwell in the house of the LORD forever." When a fellow believer dies we grieve like anyone else, but our distinct response as Christians is not "Goodbye," but "See you soon!"
2 Corinthians 5:8 KJV
"We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord."