I read this article about light and dark and how even low levels of light in the room like a nightlite can screw with people's biological clocks.

So...
I have the cable modem in my room and it's little blinking lights always shine against the opposite wall.  I put a dark handkerchief over it which made my room instantly darker, but it made me notice the green light  on the plug that goes to my laptop.
So I turn off the power strip to that and that makes me notice the power strip behind my bookshelf where I plug in my phone.  I unplug that and by then my room is really dark except it makes me notice the clock radio with it's green digital display.  Nothing another handkerchief can't fix. 
Finally, I'm almost at pitch blackness if it wasn't for the ambiant light filtering through the bamboo blinds.

I found these interesting articles about light and sleep. 

Light Pollution Raises Risks of Breast Cancer

Feature articles on melatonin at NaturalNews

The biological effects of prolonged light exposure

From that page.....

Sleep duration as a risk factor for the development of type 2 diabetes.
Men reporting short sleep duration (< or =5 and 6 h of sleep per night) were twice as likely to develop diabetes, and men reporting long sleep duration (>8 h of sleep per night [sleeping past dawn, into the light, one presumes - RJ]) were more than three times as likely to develop diabetes over the period of follow-up. Elevated risks remained essentially unchanged after adjustment for age, hypertension, smoking status, self-rated health status, education, and waist circumference…

- Diabetes Care. 2006 Mar;29(3):657-61. [15504560]

...women sleeping 5 hours or less gained 1.14 kg... more than did those sleeping 7 hours over 16 years, and women sleeping 6 hours gained 0.71 kg... more.

- [Lack of sleep in women may cause obesity] [16914506]

As astonishing as it may seem to those of us raised with ever-more artificial light from TV, video games, computers, cell phones, bedside LEDs, etc.; there is a rapidly accumulating body of evidence which suggests that extended exposure to artificial light (and therefore too little true darkness) is the largest reason why these illnesses are striking so many in industrialized and industrializing nations – this is the Photoperiod Effect.

It's not that artificial light is bad in itself, of course, but that our bodies need the true night that existed during the whole period during which we evolved. That is, we need long periods of darkness each day in order to stay truly healthy. This is because our hormone system largely controls our bodies, and night (deep darkness) controls that hormone system.

Therefore, quite new science is pointing us toward a natural path to much better health, similar to the natural food movement that brings us a bit closer to the sorts of foods our remote ancestors ate.