Several times recently I've been awakened by the subtle "ding" of my zen chime alarm clock, but have felt just exhausted. I would stay in bed for a few minutes, wondering why I'm so tired when I went to bed at a reasonable time the night before. Then after pondering, I would put on my glasses and sit up. At that point I see the clock on the cable box, only to discover that it's indeed the middle of the night and I only imagined the clock chiming. But then I'm awake, hoping and hoping that I'll fall back asleep, and that I'll have enough time left to catch some more deep somnolent time. Invariably it takes me a while, and then it seems that just when I've finally drifted off the alarm really does go off.
This morning it was 3:48 when I heard the call of the imaginary alarm. Ugh.