I've hit the Winter Wall

And it sucks!

Call it whatever you want but the Winter Wall to me is my complete lack of motivation that tends to arrive around this time every year. It happens in a similar way every year. I am going to rugby training, going to the gym (and this year riding to work) on a dailyish basis.
Then I run smack on into the winter wall.
This usually occurs, with either a cold, or an injury (this year I rolled an ankle), prior to this catalyst I can happily push through the crappy weather etc to keep the training going. However once the winter wall is hit motivation is right down, without the "forced" rigours of Rugby training and games I could easily see myself doing very, very little.
Undoubtedly a large part of the difficulty arises from the temperature and the lack of light, I can't force myself to do the usual things that help get me back into the zone. Even things that I would do in the warmer, longer dayed months no longer occur, for instance, I'm much more likely to drive to the shops after work in the dark than I am to walk or jump on my bike.
Each year I tell myself that this year will be different, but that reality is I am probably kidding myself when I say that anyway. To be honest I am fairly sure that I suffer from a particular form of SAD (or Seasonal affective disorder) and I'd say considering that I know a lot of other people that suffer from a mid-year, winter induced hiatus from exercise, or at least a large reduction in the amount of exercise performed, that it is a rather common affliction.
I can not think of a cure, I am tempted to see if I can try some sort of light therapy and I think I'll investigate it. In the meantime however it looks like I'll have to wait a few weeks and see if transporting myself into the depths of a North American summer has enough impact on the Winter Wall for me to smash a few holes in it and break on through to the other side.