Your body will hurt to its deep inner core
You know inflammation is unpleasant -- it doesn't feel good when you get something stuck between your teeth and your gums flare up. It feels even less good when you throw out your back and you're laid up for days.
But know what feels even less, less good?
Chronic inflammation that takes place inside your body, where you can't see or feel it, but where it lurks, eroding away your good health, increasing your risk for major illnesses, including diabetes, arthritis, and heart disease. And it's not just chronic sleep deprivation that does the dirty. A 2008 study found that even a single night of sleep deprivation turns on the chemical pathways that trigger your immune system to turn against you.
Oh yeah, lack of sleep also reduces pain tolerance. So when your coordination is compromised and you trip over your own feet and stub your toe on the door frame, it's going to hurt a lot worse. (This highly specific example was totally not about me.)