Found this nice gem on Ganga White’s blog via the White Lotus Foundation website.
The link is here. The italics are mine.
How Do we know we are progressing in Yoga?
Real progress in Yoga starts when you learn to see and feel, for yourself, the actual effects of the various poses. A teacher can tell you what the benefits of a pose are, but when you actually feel it yourself, it is much more effective. It is like the difference between being told what the gears in a car do and learning to use them skillfully yourself and to feel their effects on the road and control of the vehicle. As you progress, or become more effective at using the tools of Yoga, you develop the ability to articulate joints, vertebra, tendons and nerves as you tune into more subtle aspects of what the internal actions of the postures are. You learn how to remove the imbalances created by other activities and to reduce the stress we all accumulate. It’s also important to remember that the essence of yoga is about awareness and consciousness. Real progress is expressed as mental clarity, happiness, and insight into living.