Mat 26:36 Sit you here, while I go and pray yonder.
Mat 26:38 My soul is exceeding sorrowful, even unto death: tarry you here, and watch with me.
Alternative: Settle here while I depart to pray over there. I am very sad until I am put to death. Wait here and stay awake with me.

Christ knows that he will rise from the dead. Unlike most of us who face death, he knows his fate. However, he is still sad about his death, leaving his life and friends. Though he will rise from the dead, his physical life as a teacher among followers will soon be over and that life is as precious to him as it is for any of us. He is not anxious to return to heaven, as one might expect. Instead he is sad. Is he sad because he is afraid of the pain of his death? This seems unlikely. Is he sad because of what his death says about humanity? This is more likely. Is he said because some will use his death to their own ends? This is also possible.

The word translated as "soul" here means one's consciousness, one's self-awareness. It is the opposite of the purely physical body (soma), but it is also the opposite of cosmic consciousness.

It is interesting that Christ separated himself from the apostles to pray, but he still wanted witnesses. He wanted his words of prayer at his death recorded in the Gospel. He specifically ask the apostles to watch with him so that they can overhear his prayer. This didn't happen by chance.

"Sit" is from kathizô (kathizo), which means "to make sit down," "to seat," "to place," "to sit," "to recline at meals," and "to settle."

"Go" is from aperchomai (aperchomai), which means "to go away," and "to depart."

"Pray" is from proseuchomai (proseuchomai), which means "to offer prayers or vows," and "to pray for a thing."

"Soul" is from psuchê (psuche), which means "breath," "life," "self," "spirit," and "soul." It has the clear sense of the conscous self. It is also used to describe "the spirit" of things.

"Exceedingly sad" is from perilupos (perilupos), which means "very sad" and "deeply grieved."

"Even unto" is from heôs (heos), which means "until," "while," "so long as,"

"Death" is from thanatos (thanatos), which means "death" "a death sentence," and "a corpse." However, the word could be a form of the verb, thanatoô, which is the future passive of the verb meaning "to be put to death," "to be made dead."

"Tarry" is from menô (meno), which means "to stay," "to wait," "to stand fast [in battle]," "to stay at home," "to remain," "to expect," and "to wait for."

"Watch" is from grêgoreô (gregoreuo), which means "to be or to become fully awake."