I've been reading some parts from Fr. Brown's book Death of the Messiah, which is a very long and detailed commentary on the Passion narratives. He said something I found quite interesting about the agony in the garden.
He said that the Greek word the Gospel of Luke uses for this is agonia, which our English word "agony" derives from. But the Greek has a different meaning. The agon was the place of an athletic contest and also the contest itself. Agonia meant everything that went into preparing for a great athletic contest, including the tension and the foreboding and endurance. So it has a different sense from our usual understanding of agony. The idea is that Jesus was preparing for a great trial that would cost blood, sweat and tears.
Related to this, Brown explains that Jesus' initial prayer was that he might be delivered from the trial: "Father, let this cup pass." But once he received the answer that he would not be delivered, he prayed more earnestly. Why more earnestly? Because knowing that he had to endure the trial, he prayed for the strength to carry it out.
The letter to the Hebrews expands on this athletic theme: "Let us also lay aside every weight and the sin that clings to us, and let us run with perseverance the race that is set before us, looking to Jesus the pioneer and perfecter of our faith, who for the sake of the joy that was set before him endured the cross" (Heb 12:1-3)