I thought I'd take this post to explain a little bit more about how people deal with the darkness in the summer and the light in the summer. As I mentioned before, I grew up in Oslo, which does not have the extreme differences of above the Arctic Circle, but it is still noticeable.
In the summer, up north, I think that more than anything people enjoy the light and the long summer nights. The winters are so long and dark so they don't care that they don't get a lot of sleep in the summer! But of course, they will also use dark curtains or blinds to get some sleep. In Oslo, I never felt that it was a problem - I had relatively dark curtains and then sometimes I'd put on one of those airplane sleep masks.
In the winter, some people use artificial sunlight lamps to get some strong light in their lives. This is of course mainly used where the polar night period lasts for a long time. I knew someone who lived in the very north and they had one at work - every day each employee would get to use the lamp for 30 minutes.
Girasoli asked if people ski in the dark and the answer is yes. You can ski with a headlight, or go to a trail or slope with lights. Across the country there are lots of slopes and trails with lights. Around Oslo there are many trails for cross country skiing and people like to go after work so the lights are important, or they wear a headlight.