Well, we've had a few weeks to reflect on a weekend with Kino MacGregor at Moksha in Chicago. We have studied a little with Kino before, but this time we did two Mysore classes, a led Primary, and four or five various workshops (first day = nine+ hours of yoga). Without a doubt, and without much surprise, we feel that the Mysore classes are where it's at. For ashtangis, who have an ongoing, six-days-a-week practice anyway, doing that same practice in a crowded, charged environment under a skilled eye is unparalleled fun. Since it's the same practice you always do, you'd think it wouldn't feel much different. Yet, it somehow ends up being a 'ho' 'notha' level.
Kino talked about much (most?) of the discomfort (different than pain) associated with an intense practice being associated with ego. Once you develop a certain level of skill and conditioning, you are very unlikely to hurt yourself, especially when so warm, so the voice saying that you should stop comes from a psychological place. A well-known manifestation of this (in Ashtanga communities, at least) centers around backbending, which is usually the most intense part of the sequence, requiring the greatest exertion just when you are most tired, and usually prompting the deepest body sensations. It is not uncommon for nausea to surface just when it's time for backbending. There is also backbending "fever," known in Mysore as a vague cluster of symptoms (gastrointestinal distress, lethargy, emotional ebb) occurring after being taken especially deep into a backbend by Guruji (or, nowadays, Sharath or Saraswati). Ashtanga philosophy understands this as part of the psychological purging process, something that will pass if you are willing to bear it (keep practicing) rather than give into it (and back off).
This does not discount the reality of and potential for true injury, but endorses the deep, interrelated nature of the processes at work in any person. Physicality and psychology are at least intertwined and working through the acquired blocks in the body is synonymous with undoing the acquired blocks in the personality. Whether in the body or the mind, these are known as conditioning.
So, perhaps the greatest gift of a weekend of Kino's teaching was a rediscovery and endorsement of intensity. During the Mysore classes we both had the experience of practicing LONG after we hit the usual point of what we thought was exhaustion. What does that mean? It means that that previously understood point of exhaustion was actually a threshold of psychological discomfort that we had decided must be the body's limit, simply because we wanted to stop. In fact, with prompting, we discovered that the body's limits were nowhere to be found. The depth and intensity of experience bloomed once we dismissed the usually rantings in the head about stopping. Yes, yes, we must be careful not to hurt ourselves, etc. This rule (really only one end of the spectrum, one polarity) is well-known and often taken too seriously. The body is strong and can do more than you think it can. The other polarity, discovering something beyond your current psychological constructs through sheer physical exertion, is under-appreciated at best.