In order to properly appreciate the verse you mention—John 14:18—I think it’s necessary to add the subsequent two verses as well. The full passage reads: "I will not leave you desolate; I will come to you. Yet a little while, and the world will see me no more, but you will see me; because I live, you will live also. In that day you will know that I am in my Father, and you in me, and I in you" (RSV).
This is from Jesus’ final discourse to his disciples in the Gospel of John; they are sharing their final meal—the Last Supper—before his arrest. Jesus is trying to lovingly summarize his teachings and spiritual purpose and to strengthen his disciple’s faith and understanding for the challenging times that lie before them. He asks them to remember that what their senses and human minds report as "reality" in coming days will not be the spiritual Truth. They will feel alone, but he will be with them. The world will believe him to be dead, but they will know in their hearts that death is but an illusion, and his Christ Spirit remains with them.
And this great Truth does not stem from any uniqueness in him, but from the Christ energy that lives in all of us and joins us together. The message is not just that Jesus is not truly dead, but that "because I live, you live also." In that day—in the wake of his powerful demonstration—they will understand more clearly the message he’s been teaching and demonstrating: that we are all eternal expressions of the Christ, one with each other and with our divine Source.