I remember being tired every day in Jr. High and High School, struggling to not fall asleep. Once the school day was over, I'd suddenly get a huge boost of energy.
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?