There is no progress toward ultimate freedom without transformation, and this is the key issue in all lives.
B.K.S. IyengarDo not allow past experiences to be imprinted on your mind. Perform asanas each time with a fresh mind and with a fresh approach. If you are repeating what you did before, you are living in the memory, so you are living in the past. That means you don't want to proceed beyond the experience of the past. Retaining that memory is saying, 'Yesterday I did it like that.' When I ask, 'Is there anything new from what I did yesterday?' then there is progress. Am I going forward or am I going backward? Then you understand how to create dynamism in a static asana.
B.K.S. IyengarThe challenge of yoga is to go beyond our limits - within reason. We continually expand the frame of the mind by using the canvas of the body. It is as if you were to stretch a canvas more and create a larger surface for a painting. But we must respect the present form of our body. If you pull too much at once, we will rip the canvas. If the practice of today damages the practice of tomorrow, it is not correct practice.
B.K.S. Iyengar