Well, I guess I was just worn down and needed the rest. For the last four days, all I've done - really - is sleep. Sure, I've been awake here and there, but for the most part, I've just laid on the sofa and slept, watched a little tv, slept, watched a little tv, slept. I've hardly moved other than to go to sleep in my own bed. I guess I just needed it.
I'm still not feeling 100%, but at least I feel well enough to attempt work tomorrow.