When I was working 12-hour night shifts, sometimes I'd go for days at a time without seeing any sunshine whatsoever, and it used to affect me pretty badly at times, I think. Now that I'm on days it's not so bad, but I still don't like it when it's dark when I drive to work, and dark when I drive home. The datacenter where I work has no windows, so I try to make a point of going outside for at least a few minutes on my lunch break. It's actually called "Seasonal Affective Disorder," because in medical terms, your state of mind (happy, sad, angry, depressed, etc.) is known as your "affect."