When the amount of pranic energy spent is more than the body can restore, the body feels weak.  This is one way of spending energy. Uncontrolled emotions can very quickly use up the prana stored in the body.

A few minutes of anger can cost more energy than a day of physical labor. when the anger has subsided, there is still no definite command for the muscles to relax and they stay activated. When we are excited by lower emotions, the mind constantly keeps the nerves in action and our muscles tense by unrestrained and uncontrolled mental states. More of our energy is spent in keeping the muscles in continual readiness for work than in real useful work done during our lifetime.

We can compare the waste of pranic energy as the result of tension to the waste of water as the result of not turning off a faucet and allowing the water to trickle away hour after hour. So we allow our prana to trickle away in a constant stream of tension, which in turn results in wear and tear on our muscles and internal organs.

In order to regulate and balance the work of the body and mind, it is necessary to learn to economize the energy produced by our body, which is the main purpose of learning how to rest and relax. The periods of rest and relaxation help the body to rejuvenate / recharge for the next phase of work.  During relaxation there is practically no energy or prana consumed, although a little is kept in circulation to keep the body in normal condition, and the remaining part is being stored up and conserved.

Sleep is the most commonly known mode for rest and relaxation. Ideally one need 6-8 hours of rest a day depending on the life-stage, gender and other factors. Two hours before midnight and four hours after is the most advisable period for one to have a good sleep. Insomnia / sleeplessness and excessive sleep are also common diseases of 21st century. Depriving the body of much-needed rest and relaxation for long periods of time can have deleterious effects on the system. Excessive sleep on the other hand can make us dull and again have deleterious effect on our body.

The three methods for rest and relax are on three planes… physical, mental, and spiritual. No relaxation is complete until man reaches the stage of spiritual relaxation. During relaxation, the conscious mind sends a message to a particular organ, such as the heart or liver. This message is received by the instinctive mind and the order is immediately carried out. Thus one could relax all the involuntary organs too. Wakeful Sleep is an effective way to do this.

Physical: First, physical relaxation starts from the toes up and the auto suggestion passes through the muscles and reaches up to the eyes and ears at the top. Then, slowly, messages are sent to the kidneys, liver, and so on, internally.

Mental: During mental tension one should breathe slowly and rhythmically for a few minutes and concentrate on breathing. Slowly the mind will become calm and one is able to feel a kind of floating sensation, as if one were as light as a feather; one feels peace and joy.

Spiritual: Yogis know that unless man can withdraw himself from the body idea and separate himself from the ego consciousness, there is no way of obtaining complete relaxation. So, from the mental relaxation, he withdraws himself and identifies himself with the all-pervading, all-powerful, all-peaceful and joyful self, or pure consciousness within himself, because all the source of power, knowledge, peace, and strength are in the soul and not in the body.