Artists usually portray Luke's account of the agony in the garden which says that Jesus is kneeling (Matthew and Mark have him flat on the ground).
Also in Luke, an angel appears. The angel is God's answer to Jesus' prayer. And the answer is "no."
God says, "This cup can't be taken away, but I will be with you through it all." This is expressed by the angel at Jesus' side "to strengthen him."
It is then that Jesus is in agony. Only Luke uses the word "agony" - the word by which we have come to characterize this whole scene.
"Agony" comes from a Greek word describing the mental and physical tension athletes feel when facing a contest. They may be confident, but one can never be sure of all that will happen.
So the prayer of Jesus now takes a different tone. he knows he will have to face the worst. He prays that he will be able to handle it well. And he begins to sweat profusely.
Our prayers are often answered the same way as Jesus' prayer. The answer is "no" ... but God says, "I'll be with you through it all." We're grateful for God's presence, of course, but what we sometimes have to face isn't easy. It's agony.
This deserves a heart-to-heart talk. With Jesus. He's been there.