You must purge yourself before finding faults in others. When you see a mistake in somebody else, try to find if you are making the same mistake. This is the way to take judgment and to turn it into improvement. Do not look at others' bodies with envy or with superiority. All people are born with different constitutions. Never compare with others. Each one's capacities are a function of his or her internal strength. Know your capacities and continually improve upon them.
B.K.S. IyengarChange leads to disappointment if it is not sustained. Transformation is sustained change, and it is achieved through practice.
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