feeling listless

Life Another week another odd shift at work. This time eight in the morning until four in the afternoon, which means early to bed and early to rise (saw that coming surely). For some reason on this week I feel more alert in the morning, having usually only had six hours sleep. What I don't understand is why, if I try this on an ordinary week I feel dog tired at the wake up and just want to roll over. Is it work driving me out of bed. That would be wrong ...