I wish to sleep

I haven't been sleeping well for the last few nights. Ever since I slept for 11 hours on Saturday night, I've only been getting 5-6 hours a night.
Today I'm doing field work which involves leaving the house at 5:15 am. I knew I would need to get some sleep beforehand. But I screwed up. I made some crucial mistakes. And that is why I'm awake now at 3:48 am, writing this post.
Here's where I went wrong. I came home early yesterday afternoon and took a 1 hour nap to get myself a little head start on the sleep catchup. I felt good when I woke up. Then we went out for pizza and beers, except instead of beers, I drank two large glasses of Diet Coke. Stupid! How could I have been so stupid? I should know better after all these years: afternoon nap + evening caffeination = poor night's sleep.
I went to bed a little after 11 pm feeling tired and knowing at best I would get 5.5 hours sleep. Well it turns out that I just lay awake for the whole night thinking about how little sleep I was getting. I think I got about 10 minutes at one point because I had some weird thoughts that were consistent with dreaming. But that's it. Now I'm awake with a coffee in my hand, and about to watch an episode of Desperate Housewives before I hit the road.