I used to get down every single winter. For a long while, I thought I was just miserable at school or having a hard time growing up. But once I reached college, I noticed that I had a real hard time when I didn't get enough sunlight. This was especially true my Freshman year in college when there were days when I would miss daylight altogether.
My greatest discovery, other than a regular schedule and exercise, was the value of a bright light. A month ago, I purchased a
Verilux Sun Lamp. This brilliant fixture shoots out 10,000 lux of light. That's equivalent to the sun on a sunny day.
If you get the winter blues, I would highly recommend investing in one of these. Sitting in front of it for 10 minutes in the morning on a cloudy day can recharge your emotional batteries.