Why doesn't John's Gospel record Jesus' agony in Gethsemane?

Les explains that the Gethsemane agony was part of Christ's human side, not His deity side, so John can omit it. Matthew, Mark, and Luke record His agony, sweat as it were drops of blood, and His pleading with the Twelve to pray with Him. Scripture presents Him as the God-Man: total God and total man, and those natures never crossed over. Even when the average person might let the God side take over, He never did; we take by faith that He was deity and also human. This distinction helps explain differences when studying Scripture, and it connects to Paul's teaching that as Adam was the first federal head of the human race, Christ becomes the culmination, dealing with spiritual realities. The rule of thumb is first the natural, then the spiritual—first Adam, then the Christ.