Apparently severe stress, or pain, can, according to mystics, provoke/trigger an instance of what they call "descending causality", in which something comes from somewhere inside/beyond the inside of you, and out through you, washing through you, leaving changes which you might otherwise never have managed.
I think that something like this happened to me 17 years ago, and it had a dramatic effect on me. I have always described it as a "moment of grace", and only a few days ago came across this information about mystics and "descending causality", which definitely fits.
I imagine that is why so many mystics/religious types have, over the years, practised self-mortification, flagellation, privation, etc, because they hope for such an effect.
I don't know if I would go so far as to try and provoke such an experience with self-inflicted pain/stress, but I can understand the desire. It was an amazing, and beautiful and utterly transformational experience. It all started with the worst headache I have ever had in my entire life.
I have had a child, and didn't use any painkillers, just breathing techniques, and my body's natural painkillers, which are produced in huge quantity as labour approaches. That was more like detaching myself from the pain, letting it go, opiated out, whereas the headache ... I "suffered" it, fought it, avoided it, struggled with it, ... for hours.
Generally I avoid pain. Low threshold to it.
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