Mark 14:36

And he said, Abba, Father, all things are possible to thee: remove this cup from me: howbeit, not what I will, but what thou wilt.

Of course, God could have removed the cup; but to have done so would have enthroned Satan as the Lord of man, and the destruction of all men would have resulted at once. Reading the character of Satan in both the Old Testament and the New Testament, one is compelled to see the destruction of God's human creation as a prime objective of Satan, reaching all the way back to Eden; and, if Christ's redemptive death had been aborted, absolutely nothing would have stood in the way of Satan's total achievement of his goal. See my Commentary on Hebrews, Hebrews 2:14.

Howbeit not what I will, but what thou wilt ... At such overwhelming cost to himself, the Lord consented to the Father's will, despite the agony within himself. Here, in the garden, the human nature of our Lord was, for a time, in the ascendancy; and the final put-down of the flesh was achieved at the price of the agony detailed in the Gospels.