Puzzled... By Sleep

I often have insomnia... After five hours of sleep, I wake up, ready to begin my day. If I get up, I feel great - energetic. In fact, I often do my laundry and other household tasks.














But (and this is what puzzles me)... if, after puttering around for an hour or two, I feel tired again and decide to catch a little more sleep, I have no problem falling asleep. BUT... when I wake up after that, I feel AWFUL! Listless and lethargic... NO ENERGY WHATSOEVER....

(Shouldn't it be the opposite?! Shouldn't I feel better?)

What I want to know is: WHY?!