Because he knew his time was up and he felt he hadn’t accomplished what he had intended to do. Jesus put his best effort in Peter and even he (peter) didn’t get the message. Jesus needed more time and he didn’t have it. Remember when Jesus was in the Garden praying and asking that the ‘cup’ be taken from him and the disciples couldn’t stay awake? That cup was the Spirit of Wisdom (my own words) that he had and hoped to pass on to one of his disciples and carry on his work; but none of them was worthy. After Jesus was crucified all of the male disciples scattered and didn’t know what to do. It was Mary Magdellan that still had the faith, knew the message because she was the only disciple who personally understood the message. She had 7 demons cast out of her by Jesus; she is the only one that truly benefited from the power of Faith. And like Vee27 said, he was experiencing life as a human and not the Messiah.
I dont think that He felt as if He hadnt done enough on earth, or that He needed more time. If you were Christ, would you want to be crucified? It is a true form of torture, whipped, torn, spit upon, suffocating, back stuck on a tree that if you wanted to breathe, you had to scrape along, and get splinters all on your already beaten and whipped back? No, you wouldnt. Theres more to it than that, but would you be looking forward to your own crucifixion? And He didnt want to pass on His death to one of His disciples, He was and is the only sacrifice that will give us salvation. Even though the disciples scattered, they came back together, and worked for the glory of Christ. They were scared, wouldnt you be? I dont think you have quite the right story...
On earth, he was complete human and as a result of that, he became afraid knowing what he had to go through, the fear of pain, the fear of rejection etc. the thought of it all made him cry.
Think he had the sin of the world on him all it even till now he carried all that sin how do think that would make you feel?
Was he crying or it was sweat in the form of tiny litle drops of blood out of agony?