He was not bothered about the pain that will be inflicted on his body but the separation between him and his father.
He said "I and my father are one" but on the cross he cried out to the father and there was no help as result of our sins which he carried. There was a separation between them.
And about the ninth hour Jesus cried out with a loud voice "Eli , Eli , lama sabachthani?" that is , "My God , My God , why have You forsaken Me?" Matthew 27 :46NKJV
Separation is really painful, think of it this way: when you lose a dear one or when you complete school and about to leave your great friends.
Since separation is painful, God doesn't want us to be separated from Him for whatsoever reasons and so He tells us:
Abide in Me , and I in you. As the branch cannot bear fruit of itself , unless it abides in the vine , neither can you , unless you abide in Me. "I am the vine , you are the branches. He who abides in Me , and I in him , bears much fruit; for without Me you can do nothing. John 15:4-5NKJV
Without God you are nobody and so don't ever disconnect yourself from God.
Always connect to your source: Jesus Christ.
