(Almost) A Full Nights' Sleep!

So Ella slept through the night for the first time last night! She fell asleep around 8:30 pm, I fed/changed her before I hit the sack around 11 pm (she remained asleep the entire time, mind you). It was so bizarre, I actually woke up around 4:30 this morning thinking something was wrong! I raced into her bedroom to find her sleeping peacefully, where she remained until 6 am. The question I have now is this: WHY AM I STILL SO TIRED??! It seems that no matter how much or how little sleep I get, I still feel the same level of exhaustion. I'm assuming this is what other mothers are referring to when they say you'll never get a full nights' sleep again, even if your child does. Bummer! Oh well, let's just see if we can get a repeat of this glorious event tonight!