My mother (age 93) still uses her Southern North Carolina affectations . . . . When she feels good, or is happy, she is in "High Cotton" - from the term for good crop harvest; when she is not feeling well, she is in "Low Cotton" as in, "How are 'ya doing today mom?" - "I'm in low cotton this morning."
The term "high cotton" or "tall cotton" originates from the rural farming community in the antebellum (pre-Civil War) when "high cotton" meant that the crops were good and the prices, were, too. The term has generalized to mean one is doing well or is successful.