The battle of yoga is with the body and with the ego. You must conquer your ego, or small self, so that you can let your soul, your big Self, be victorious.
B.K.S. IyengarWe can wash the skin of our bodies with a bath, but through asana practice we not only purify our blood and cells, we are cleansing the inner body as we practice.
B.K.S. IyengarAs a fire blazes brightly when the covering of ash over it is scattered by the wind, the divine fire within the body shines in all its majesty when the ashes of desire are scattered by the practice of pranayama.
B.K.S. IyengarYou must do the asana with your soul. How can you do an asana with your soul? We can only do it with the organ of the body that is closest to the soul - the heart. So a virtuous asana is done from the heart and not from the head. Then you are not just doing it, but you are in it. Many people try to think their way into an asana, but you must instead feel your way into it through love and devotion
B.K.S. Iyengar