To understand this powerful, life transforming truth, we need to understand about this stuff of which the dream world and this world are made of. We need to know about prana, the life energy that sustains us.
Understand, the air you breathe is just a vehicle in which the prana comes in and goes out. Prana is the life force, the energy itself. Understand this one example. If a truck comes inside this campus and leaves something and goes out, the truck is like the air, the breath. The product that is delivered is prana.
Dreams are made of the same stuff of which this waking world is made. Constantly, the air is going in and leaving the prana inside and the air is coming out. Constantly, we are taking prana through air. In India, if you attended Kumbh Mela, the largest spiritual gathering in the world attended by millions of people, you may have seen the yogis bury their heads totally in the earth for three days. They are able to do this because they know how to take the prana into their body directly from the cosmos without the help of air. As long as you take prana through air, you need to breathe through your nose. You need to inhale and exhale. But, when you can take the prana directly without the help of air, you don’t need to inhale or exhale through the nose. Your body can directly take the prana through the cosmos.
One more thing: as long as the incoming breath is bringing in more prana and going out as an empty vehicle, your life will be strengthened. If the reverse starts happening, if the air comes with less prana and goes out with more prana, it means death is nearing or the life energy is going towards death. When death nears, just the empty air will enter but when it goes out, it will go with the prana. That is the reason all the great masters, such as Buddha, Shankara, Guru Nanak, and Mahavira, knew or could sense the prana and they could predict their death. Six months before their passing away, they were able to see very clearly the prana moving out of their body.
There is a beautiful concept in Ayurveda* called as the ‘peak age’ which is based on this science of prana. Till a particular age, the person will be receiving more prana through the incoming breath and less prana will be going out through the outgoing breath. The moment the outgoing breath starts carrying more prana than the incoming breath, they know now the person is moving towards death.
The prana moves, functions, and stays in the ajna chakra when you are in the waking state. When you are in the dream state, it moves around the neck, around the vishuddhi chakra. When you are in deep sleep, it moves around the anahata chakra, heart center.
That is why you can never fall asleep if your head is erect. You cannot fall asleep unless you relax the head, unless you allow the prana movement to move from the forehead to the heart region. That is the reason why you can’t sleep unless you relax your head. Even if you are lying on the bed, if you keep your head straight and tense, you will never be able to fall asleep.
If you think constantly, your head will be erect and your shoulder will be under stress. The stress in the shoulder and the head being erect are very closely associated. You can see this in your life. When you reach your office in the morning you don’t have to do any work. Just sitting in your chair and thinking about the problems will stress you and you will have shoulder pain!
Actually all the pain and the stress you experience first in the shoulder only. When your shoulder is under stress, the head will never bend, the head will never relax. That is why people who think constantly can neither relax their head nor will they be able to fall asleep.
source: Living Enlightenment