Jekyll and Hyde? Or Ari and Ari?

What a difference a day makes.
Yesterday, Ari was a perfect angel, as he usually is. Fearing he would freak out getting a hair cut, he was the perfect child - he sat still in the chair, let the lady cut his hair and even admired himself afterwards.
Today, after a night of broken sleep (highly, highly unusual), he's a contrary little boy. He doesn't seem to want to eat much, or behave himself. It's incredibly frustrating as he's suddenly become a little boy I don't know and don't know how to handle.
Worse still, I've had to let him cry himself to sleep, which I hate doing. He just desperately needs to sleep, which is why he's being a little terror. I feel like the worst mother right now, but I know it's for the best.