I can't even say that its because I've been going to bed later.
~Grumble~
I've been in bed by 11 or midnight everyday for the past week.
I swear it has to do with the lighting where I'm working. Until next week or possibly later this week, I've been working out of my boss' house. We're going to be moving into a new office soon, but he keeps the house so dark. Oddly I'm not sleepy when I'm at work, but once I leave I feel like a ton of bricks has been dropped on me.
Two Beatles songs keep sticking in my head when it comes to this; I'm Only Sleeping and I'm So Tired. Must quit yawning, yawning only makes it worse.

Aw great, the smiley is even yawning. This is not good. All I need now is a pillow and a blanket and I'll be fast asleep on my computer. Hmmmm

Well at least the smiley is getting a nap.