“When the breath is irregular, the mind is unsteady, but when the breath is still, so is the mind still and the Yogin obtains the power of stillness. Therefore the breath should be restrained.” (Hatha Yoga Pradipika)
The breathing exercises in yoga are called Pranayama - Prana means the body’s vital or psychic energy, and yama to control or master it. The Yoga Sutra by Patanjali, says: “Pranayama is cessation of the movement of inhalation and exhalation” and “thus the covering of the light is dissolved and the mind is fit for concentration.”
In certain breathing exercises one inhales completely and holds the breath and in others one exhales completely and holds the breath. In deep meditation or relaxation, the breath can become gradually fainter and eventually stops for a while. This is described as the highest form of pranayama. In his book, “The Holy Science,” Sri Yukteswar maintains that holding the breath calms the autonomic nervous system so that the inner organs also get to rest.