can't sleep (again)

It'd be awesome if I knew why I can't sleep. I went to bed 2 hours ago and recently got back out of bed because I found it pointless to keep lying there. *sigh* And it's not like I did nothing all day, which generally does make sleeping difficult. I was actually really productive! I did my bankruptcy homework for the rest of the week, I worked on my 3L paper, and I started studying Mergers & Acquisitions. All of this on top of a workout (cardio and weights) and going out to dinner. So I certainly used up energy today and have thus not answered the question why am I still awake... I WANT TO GO TO SLEEP!