Harmony is at the center of your health. You need harmony in the food you eat. Excess in certain nutrients and deficiency in others causes disease. The same is true for exercise. As elaborated above, movement itself requires the harmony of strength (the ability to hold) and flexibility (the ability to move).
However, too much movement (i.e. work or stress) will deplete you, so the necessary counterbalance is adequate rest. Your body and mind need recharging to work optimally.
In practical application, you should receive adequate rest each night as well as adequate time daily to rest your mind. Taking breaks between periods of work is essential to produce top quality work; this is true for both professional and athletic work. Meditation and recreation is another method for ensuring your body and mind receive the rest they require because the mind will begin to degrade with excessive movement as well.
Sleep is defined as:
a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, inhibition of nearly all voluntary muscles, and reduced interactions with surroundings.
To get quality sleep, what you are really doing is relaxing your mind and body from an active/focused state to a passive/relaxed. To do this, there are two strategies you can use.
Rituals (building cognitive patterns and associations)
Resolve Your Inner Dialogue
A Peaceful Mind