What does the line "I can't do it" in the second chapter of The Sun Also Rises mean?I want to know what it refers to.

In Chapter II of the book, Robert Cohen is sleeping in the office.  When Jake Barnes goes to wake him up, Cohen says "I can't do it."

To me, this statement is meant to refer to being content with one's current surroundings and life.  Jake and Robert have just spent the whole chapter talking about why Robert is unhappy and why he can't just be content to stay in Paris.

Since this is what the whole chapter has been about, and since this inability to find happiness is one of Robert's main traits, that is what I think he is referring to when he talks in his sleep.