Playing Sport and SAD

I've only recently recognised that I suffer from the symptoms of SAD (I did something about it last year) and I felt firmly rubbish last week, so have started my light treatments (I use a Philips EnergyLight for those interested - the one that looks like a giant Tic-Tac).

I have a full time job and have made a concerted effort to get fit to play basketball for this season at a high level (training throughout the Summer). The thing is, having put so much time and effort into practice, it's very frustrating to find that my focus on the goals I have is blurring, the motivation to eat the right food is dropping away, and, by the time I finish a working day and get to practice, I'm too tired to play at the level I know I can.

Please note that I've desperately tried to find ANY other reason for the way I feel (I just can't feel comfortable giving in to having this type of condition, although I try hard!).

Can someone else with SAD and a love for sport please let me know by reply to this topic? It would just be good to know that I'm not alone with this frustrating situation.....

I'm quite a keen cyclist, during summer 30-50 miles on a satarday morning, 15-20 a few evenings a week.

Now dark days and dark nights I really do lack the motivation to get out. However if I do force myself to get out I do feel the benefit.