Breathing should come naturally, it is after all an involuntary action of the body essential to survival and a balanced autonomic pervious system. Holding the breath is also an involuntary response to stress, that ultimately leads to more stress, physical pain, and living in state of sympathetic nervous system dominance (ie. Fight or flight). Breath itself has a mystic quality. Healing and spiritual traditions all around the world have independently realized the power of the breath to heal.
