I remembered what the third thing was! (please see previous post)
I heard of what seemed to me a rather good insomnia suggestion that I had never heard before. Happily, I'm not suffering much from that particular problem these days but I'm ever on the alert for new ways to deal with it when it does arise. True, the fact that I'm typing this at 12.22am might seem to belie this assertion but I'm staying up all night on purpose, which is dangerous, I know, but I haven't done it in an age and I don't want to stop working when I am so damn close to being done. The end is tantalisingly close and I really, really childishly want to be the next person to put 'dissertation finished' as a facebook status update. I know how silly that is. I'm also terrified that I won't finish in time - I've been having a horrible time trying to work for the past two weeks and I really want it to end. Tangential self-excusing over now.
The suggestion is this: if you cannot sleep and you know you're not going to sleep, try to spend some of your time meditating. The meditation is not meant to relax you so that you can then go to sleep but rather as an obviously inadequate sleep substitute that is clearly a hell of a lot better than pacing, poking around on the internets or watching television. That way, you can have some rest even if you can't have sleep.
Whilst it's not a viable option for all and any kind of sleepless night, it really appealed to me as a positive option. I like that it is something that is not intended to lead to sleep but rather to ameliorate sleeplessness. It's perfectly possible to follow all of the good, long term habits for sleep and still not be able to sleep: I'm pleased to now have sleep-loss amelioration suggestion.