Sleeping on a problem works. Studies show a positive correlation between sleep and cognitive function. Contemplating a problem and then “sleeping on it” can result in better problem solving
Sleep is a period of resting the body and mind consisting of repeating REM and non-REM patterns and distinguished from wakefulness, hibernation, or comatose.
The old saying “feed a cold, starve a fever” has truth to it, but generally you should feed a cold and a fever and starve neither.
Exposure to light in moderation, especially natural sunlight, can have an uplifting effect on mood, while excessive darkness can have the opposite effect.
Studies show you can semi-effectively catch up on short-term sleep debt over a few nights, but not long-term sleep debt accumulated over time.
Artificial light changed sleeping habits. People used to sleep in two phases, “first sleep” and “second sleep”, with two hours of awake time between.