I haven't quite gotten to the bottom of the reason, but at the moment I am itching to go running. This would / should be a great thing however I am lacking energy. There are several possible reasons and I can't decide which is most to blame (or if it is a conspiracy of all of them). Firstly, there is the diet plan / calorie counting which I think is the lead candidate given that I have lost 6lb in two weeks. Secondly, there is the possibility that one of my lovely offspring has passed on a bug, also quite likely as the youngest is teething just now. Thirdly, there is lack of sleep, which is always a strong contender in these matters (multiple reasons for sleep debt, not least watching late night news about the recent English riots). Fourth, work, but that is an ever present and can't really be put in the frame.
Whatever it is I will try to run this evening it see how I feel, and try to blow a few cobwebs away. Perhaps while I'm zoned out during the run I'll figure it out.