The cave environment is quite different and requires some adaptation. The first time I was underground for more than two hours, i began to feel very oppressed, just thinking of all the solid rock that was above me.. With time and numerous trips, that feeling went away.
Getting used to squeezes is the same sort of thing. Gradual exposure gives you an idea of where your limits lie. I got better at it, but not nearly as good as some of my caving fanatic friends - they would perfect their skills above ground by crawling through chairs.
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Geezer in Chief