The main reason why pranayama is one limb of only eight limbs in ashtanga yoga is because of the role that kumbhaka (breath retention) plays in concentrating awareness and contemplating the mind. Retaining the breath is a principle means of restraining thought, of brininging about the ultimate goal of yoga: "citta vrtti nirodha," the ceasing of the turnings of thoughts.

If to retain the breath is to restrain the mind, then to successfully practice pranayama is to pierce through to the heart of yoga, to transcend the activities of the mind. Then also the practice of kumbhaka is less about breath control and more about mental control, about learning to stop the breath as a means of learning to stop the incessant activity of the mind.