A really brilliant tool for SAD is a light box. I have had mine now for 3 years, turn it on for an hour or so in the morning, and it should help. There is a SAD site that gives you all the information you need relating to this condition that I found absolutely brilliant, including why light therapy works, how, where to buy a light box, best ones to use and how to use them. For a little over £100 it has made me so much more confident about facing our gloomy, wet English winters !! And the funny thing is, I keep mine in work, and its amazing just how many people gravitate towards it !! I think SAD affects an awful lot, to varying degrees, very few people actually enjoy winter, cold and dark mornings and evenings, its like living like moles, and we're not moles !!!
The other thing that helps, is to just go out of the office environment at lunchtime, whatever the weather, for twenty minutes or so. The light box works on the same principals as what that exposure to whatever bit of daylight there is, and the website again tells you why this is.
My gp wouldn't diagnose the condition until it was found that I had these awful symptoms for 2 winters, but if you thnk you may suffer from it, treat yourself to a lightbox !! You can also prepare for it too, by using it from about October. It changed my life !!
Hope this helps
Sue