Adjusting to natural light
In a sense, web design can be seen as a light acupuncture against the rods and cones of the user's eyes. (Just a weird opinion.) Every web designer that spends a lot of time in front of a monitor is effectively in a relationship with the light it is emitting. It can affect our mood, it can cause headaches in case of overdose, it can prevent us from easily falling asleep at night. We seem to be more sensitive to brightness than to contrast. In low-light surroundings, the brightness of a monitor suddenly starts to feel much stronger and stimulating. Light intensity affects how we perceive colors too, which is why in such conditions they will feel more saturated. Even if we carefully plan the look of a website, we can't be certain that the user will be exposed to the same lightning conditions. It's more likely that he/she will perceive things slightly differently.
We often take light for granted and use all kinds of light sources at night and roller blinds during the day (especially when sunlight interferes with screen light). But just because something is possible, widely-accepted or not questioned doesn't mean that we should necessarily do it. If we use light sources at night or blinds during the morning hours, we disconnect ourselves from the cycle of day and night and the calm that it can instill in us. We also start to perceive things differently, while—in effect—we are trying to change what nature already tells us. Simply walking around and thinking in the dark can give us ideas we wouldn't come to if we stayed close to a light-emitting surface all night. With no light, our body functions start to naturally slow down, we feel more in peace with ourselves and can feel better the hopes for another tomorrow, to really anticipate it. If you don't believe me, try to not use lights for a day and see how you feel.
An equal effect we can have in the mornings. Our body can be very alert to light sensitivity and we can wake up as soon as the first light rays hit our place. If we have our blinds open, the body will find its natural rhythm and can surprise us that it can be almost as precise as clock. I could wake up three days in a row with a time difference of only two minutes, which amazed me. It seems that the alarm-clock is another technology we don't necessary need, that is only producing stress. We get more precise with time, when we naturally go to bed and wake up at the same hours of the day.
During the day, one of the best ways to increase our energy levels is to expose ourselves to more natural light. Simply spending some time walking in a park with a great company can change how we feel and recharge us. Probably more than anything else, how we currently feel affects our work, so we need to be aware of what our body is telling us. It's only when we feel good that we can do good work. Adjusting to natural light and smiling to it gives us an opportunity to see that there's another world outside our monitor.