Hatha Yoga teaches us to use the body as the bow, asana as the arrow, and the soul the target.
B.K.S. IyengarYes, flexibility of body and physical perfection for Yogasana is important. However more important is the state of your mind, Meditative mind. Your flexibility might be excellent but if your mind is not attentive, you are merely doing some physical exercise, not Yoga.
B.K.S. IyengarWhere does the body end and the mind begin? Where does the mind end and the spirit begin? They cannot be divided as they are inter-related and but different aspects of the same all-pervading divine consciousness.
B.K.S. Iyengar