Am I the least energetic person on earth?

Yesterday, I ran some errands and then drove out to my parents' house to meet and hang around with my sister, brother-in-law and nephew. I left the house around 10 am and returned about 12 hours later. As days go, it couldn't even be characterized as mildly hectic, yet today I feel utterly spent. Then I read this. The mind boggles. Just reading it is exhausting. And this is a woman who just had a baby--her fourth. Is it nap time yet?