I always hated that. Sitting in a warm room, a lecturer drones on in a pleasant monotone, I fight to keep my eyelids open but they just feel so heavy, I need to

I always hated that. Sitting in a warm room, a lecturer drones on in a pleasant monotone, I fight to keep my eyelids open but they just feel so heavy, I need to sleep... Then, class is over, step outside, BAM. Fresh and awake. WTF, body, why couldn't you be this alert when it mattered?