I was a pm (3-11) nurse for many years & worked my share of nights (11-7) too. Then I worked days for many years after that. Now that I'm retired I find myself falling back into my pm persona - I get a second wind after supper & can sew or read into the wee hours of morning. Or just sit on the deck in the dark watching the stars. I guess everyone has their own internal rhythm & that must be mine. I makemyself get up at 7:30 though no matter what. It is soooo awesome being retired!