Sleeplessness

Why is it that one good night of sleep, followed by an entire day of feeling awake and not tired, almost always results in insomnia the following night? I finally managed to wake up this morning (after ten hours asleep!) without feeling that the thing I most wanted to do was to crawl straight back into my bed and curl up under the covers. I had an entire day of not feeling tired! I did some work and took my library books back, and bought about a million file dividers. In the evening I went out for a while with some PGCE people. It was nice to see everybody, but there was a lot of alcohol... so I sloped off quite early and came home to talk to Noah. Then, feeling pleasantly sleepy, I headed to bed. But alas! It was an illusory somnolence! Here I am a couple of hours later, wide awake, drinking hot chocolate and trying to write something coherent about Vygotsky. It's not fair!