Nine years ago, on the advice of my mother, I bought a full-spectrum light from a company called Verilux and put it by my desk when I spend most of my work days. It's not technically a "happy light" (which is a specific type of full-spectrum light that is designed for maximum light output) but a lamp that shines on my hands and arms as I type. But it seems to be enough because either because of it, or a psychosomatic effect, I feel better. I haven't suffered from SAD since I got it.
When I needed a light for reading, I also got a full-spectrum light. I figured it couldn't hurt to have more full-spectrum light.
So if you have the "winter blues," I strongly suggest that you get a full-spectrum light and put it where are are the most.
Do you have a full-spectrum light? What are your experiences with it? Let me know in the comments below.