"I speak this in the world so that they may share my joy completely"
When he had said to his Father: “And now I will no longer be in the world...; I am coming to you” (Jn 17,11), our Lord recommended to his Father those who were about to be deprived of his physical presence: “Holy Father, keep them in your name that you have given to me.” As man, Jesus prays to God for the disciples he has received from God. But note what follows: “So that they may be one just as we are.” He does not say: That they may be one with us, or: So that they and we together may be one thing just as we are one, but he says: “That they may be one just as we are.” That they may be one in their nature just as we are one in ours. The truth is that these words imply that Jesus spoke as having the same divine nature as his Father, as he says elsewhere: “The Father and I are one,” (Jn 10,30). According to his human nature he had said: “My Father is greater than I, “ (Jn 14,28), but since God and man form one and the same person in him, we understand that he is man because he prays and understand him to be God because he is one thing with the one to whom he prays...
“But now I am coming to you. I speak this in the world so that they may share my joy completely.” As yet he has not left the world; he is still there; but since he is shortly going to leave it, he is no longer in it, so to speak. But what is that joy with which he wants his disciples to be filled? This he has already explained a little before, when he said: “That they may be one as we are.” Concerning this joy, which belongs to him and which he has given to them, he foretells to them the perfect fulfillment and that is why he speaks about it “in the world”. This joy is the peace and happiness of the world to come and, to gain it, we must live in the present world with self-restraint, justice and devotion.