On another board, I read several folks say that getting one of those, sitting
in front of it every day for a certain period of time helped them a lot. They also reported that dark winter days are more difficult for them than seasons with more light.
If you have flexibility in where you live, and if you find you are affected by the presence/absence of natural daylight, you might consider moving. I've met a few folks who moved to the southwest of US for exactly that reason.