Do not allow past experiences to be imprinted on your mind. Perform asana each time with a fresh mind and with a fresh approach.
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. Iyengar