"It is not enough to feel pain and push through; actually pushing through some types of pain is pure insanity. Instead pain is your teacher on a much deeper level that forces you to dig deep into the heart of yoga... Pain is your motivation to learn healthy alignment, better technique and more efficient movement patterns. If the way that you approach your physical body leads to injury and suffering it generally indicates that it is time to use that sensation to motivate yourself to try a new method of movement. Many people take their first experience of pain in yoga as a sign to change styles of yoga, but if the deeper question of technique and alignment is not addressed the same injury will just reappear later. If you can recognize pain as a signal to retrain your movement patterns to an empirically sound method then you will find a new freedom in your yoga practice. Rather than jumping ship from one style of yoga to another the best course of action is to use your rational mind to learn a new approach to the postures and movements that give you pain. Discovering a healthy use of the body and making small adjustments to your approach will alleviate pain caused by unhealthy movement patterns. If you listen and change your approach the pain eventually disappears. When yoga says that pain is your teacher it does not ask you to plow through blindly. Instead pain is your motivation to make the changes in your technical approach to movement in order to be healthier and ultimately free from the kind of pain that will injure you."
As I was reading this passage, I thought about how ashtanga "enjoys" a bad rep among certain segments of the yoga community. I don't know the exact cause of this bad rep, but I think there are a couple of possible reasons for it. First, I think a big part of this bad rep has to do with the fact that people hear so many stories of ashtangis (myself included) who get this or that injury from doing this or that posture. I think it is quite understandable for people to react this way. A big part of the responsibility actually lies with myself: It is I who has injured myself because I did not bother to listen to what my body was telling me, to use my rational questioning mind to "learn a new approach to the postures and movements" while "making small adjustments to [my] approach [that] will alleviate pain caused by unhealthy movement patterns."
Looking at the same matter from another angle, we can also see whatever pain the practice brings up in our bodies as messages telling us that our bodies need to move in some other more optimal and efficient (and less painful) way. In this sense, pain is a teacher; it helps us to take the necessary actions to be more at home in the practice. If we react to pain by "jumping ship" to another style of yoga, the underlying imbalance or unhealthy movement pattern that caused the pain won't simply go away: It just stays right there, waiting to resurface at some other time and occasion.
This brings me to another possible reason for ashtanga's bad rep. It is usually expressed in this way: "I dislike/hate ashtanga! It's so rigid! Why do I have to do these postures in this particular sequence, and no other? I hate forward bends and hip-openers! Why do we have to do so many of them in the primary series?" But I think there is a reason why the postures of the primary series are arranged the way they are: They are arranged in that way to challenge us to "learn a new approach to postures and movements", to find a way to work through a particularly demanding sequence of postures with optimal comfort and minimal pain. The Yoga Sutra says, "Sthira Sukham Asanam", which can be translated as "Asana is steady exertion with ease, comfort without dullness." In my opinion, the challenge of the ashtanga vinyasa system is to enable the practitioner to attain sthira sukham asanam within the constraint of a set series of postures. Far from limiting our freedom, this constraint actually gives us a well-defined space within which we can fully realize the power of our mind and body by squarely and unflinchingly confronting and surmounting our limitations.
Of course, there is a sense in which anybody can find his or her own freedom if he or she were to just fashion a sequence of postures consisting only of postures with which they are totally comfortable, which they can easily work with. The question is: How much would such "freedom" be worth? The Indian poet Rabindranath Tagore says, "Emancipation from the bondage of the soil is no freedom for the tree." Similarly, we can see the demands of the primary series as the "soil" through which our mind/body has to break through in order to attain true freedom; a freedom which is deeply and firmly rooted in the soil of tapas, a freedom which can stand tall and firm in the face of the winds of adversity. Conversely, I think we would be well-advised to be wary of any promise of "freedom" which purports to give us liberation without the trials and tribulations of constraint and boundary. Such freedom, enticing as it may seem, may come only at the price of depriving us of the valuable soil which we need for our growth.