I'm not sure what happened, exactly, but at some point some time very recently, I did something that screwed up my sleep schedule. It's weird, because for my new job I have to stay up later -- and I've only had two shifts, but it's not like either of them had me going to bed earlier, but I'm still getting tired around 8:30.
Maybe it's just the winter. Or maybe I'm undersleeping. Either way, I'm going to go to bed now.