Insomniatic Tendencies

Am I the only one who has trouble sleeping, not necessarily because of too much stress or emotional turbulence, but simply because you constantly have a list of things you need to do running through your brain? Last night, for example, I was laying in bed, completely exhausted, but couldn't fall asleep because I just remembered that I needed to call my dental surgeon, and then remembered I needed to e-mail a course instructor, and a few other things. I actually tossed and turned, despite how much I wanted to sleep, because I kept thinking "Oh no, if I sleep, I might not remember in the morning. I should write it down. Oh shut up, Alex, you'll remember. Go to sleep. No I'll probably forget..." And on it went until I finally gave in and wrote out an entire to-do list with everything I needed to accomplish and every person I needed to call. All I want to do is sleep. Why can't my brain start filing a little earlier in the day?