Albert Barnes on Matthew 26:38

My soul is exceeding sorrowful. His human nature-his soul- -was much and deeply affected and pressed down.

Even unto death. This denotes extreme sorrow and agony. The sufferings of death are the greatest of which we have any knowledge; they are the most feared and dreaded by man; and those sufferings are, therefore, put for extreme and indescribable anguish. The meaning may be thus expressed: My sorrows are so great, that under their burden I am ready to die; such is the anxiety of mind, that I seem to bear the pains of death!

Tarry ye here, and watch with me. The word rendered watch, means, literally, to abstain from sleep; then to be vigilant--to guard against danger. Here it seems to mean, to sympathize with him; to unite with him in seeking Divine support; and to prepare themselves for approaching dangers.

(h) "My soul" Ps 116:3, Is 53:3,10, Jn 12:27