Just listened to an interesting interview with the author of All Joy and No Fun - described as "a book about parental well-being."

She said that parents divide into groups depending on how they react to protracted sleep deprivation: 1/3 are OK, 1/3 are compromised and cranky and 1/3 are catastrophically affected.

http://www.npr.org/2014/01/24/265365876/a-parenting-paradox-how-kids-manage-to-be-all-joy-and-no-fun

I'm a category 2... although if there were a category 2 1/2, I feel like that would better describe my reaction to sleep!