Mat 26:40 What, could you not watch with me one hour?
Mat 26:41 Watch and pray, that you enter not into temptation: the spirit indeed [is] willing, but the flesh [is] weak.
Alternative: Are you not strong enough to stay fully awake with me one hour? Stay away and offer prayers: divine inspiration is truly ready but the flesh is feeble.

Christ used the term used here for "spirit" in the positive sense to mean the breath of God, divine inspiration. In the negative sense, it means the spirits of madness that can control a person and must be thrown out. The concept captures the changes in our attitude, temperament, or inspiration which can either uplift us or bring us down.

The word is different the word used for "soul" in Mat 26:38. While both mean "breath," the spirit here is more of a force: a wind or a blast. While our soul is our awareness and consciousness, the spart of life within us. This "spirit" is the internal pressure that motivates us, the breath of God or the climate of society. This latter is the type of spirit than makes people into "beggars of spirit" as referenced in the Beatitudes.

The word used for "flesh" here is also not the word that Christ used for "body" in Mat 26:26 (discussion here). The "body" is the physical part of a person without their soul, but in the Greek the word for "flesh" here (sarx) has an even lower sense, that of being just meat, but Christ doesn't use it that way. He uses this word "flesh" as symbolic of the relationships between people. It is the flesh and blood people we get information from (Mat 16:17), the flesh that unites husband and wife (Mat 19:5), and the flesh for which the last days are shortened (Mat 24:22). There is a sense in Christ that these relationships like our bodies are very important but "feeble."

In the last few chapters, the original Greek focuses on the idea being awake and ready. In English, this is lost because the term for awake is often translated as "watch." One way to read this is that divine inspiration keeps us ready but the weakness of our earthly bonds to God make it hard to keep connected with that divine breath.

"Could you " is from ischuô (ischuo), which means "to be strong in body," "to be powerful," "to prevail," and "to be worth."

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

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

"Temptation" is from peirasmos (peirasmos), which means a "trial," "worry," and only by extension "temptation."

"Spirit" is from pneuma (pneuma), which means "blast," "wind," "breath," "breath of life," "flatulence," "divine inspiration," and "immaterial beings."

"Willing" is from prothumos (prothumos), which means "ready," "willing," "eager," "bearing goodwill," "wishing well," and "readily."

"Flesh" is from sarx (sarx), which means "flesh," "the flesh of fruit," "the body," "meat," and "the physical order of things."

"Weak" is from asthenês (asthenes), which means "without strength," "weak," "sickly," "feeble," "poor," and "insignificant."