The Communion verse at today's Mass is John 6.51: "I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world." What's stated is crystal clear (unless you don't listen or just try to figure out what you think it should mean). I know I am going to live forever, not because I am extra holy or arrogant in any way, but because I trust in what Jesus had said plainly. I believe that the bread he had given us in the Holy Eucharist is his flesh and I do eat this bread at Mass every time. Therefore, I shall live forever as he had promised.