Why is breathing so important an aspect of virtually every world spiritual discipline? There is at least one simple physiological reason (and yoga suggests that the safe entrance to the realm of the spirit is found in only two places: the body, and the heart). That reason is that breathing is the only physical process that is both voluntary and autonomic. As you slow your breathing down to below about 4 breaths per minute, you will begin to feel discomfort as the oxygen/carbon dioxide balance begins to shift. That discomfort is your body saying "hey! Cut that out." The resultant stress is very very similar to the stress caused by anger and fear. If you go deeper, slowing the breathing to below about 3 breaths per minute, this deepens. To relax sufficiently to reduce the body's need for oxygen, simultaneously "turning off" the CO2 alarm, is quite an accomplishment. That skill overlaps greatly with the ability to deal with other life stresses with elegance and grace. And especially, to deal with fear. Fear is the great destroyer: fear of failure, success, separation, anonymity, fame, initmacy, lonliness, and especially death of body and ego. Conquer fear, and you conquer your life. This is a gross overview of the power of learning to control breathing. We'll go into more subtle aspects of it another time.