I would like to talk a little bit about pain. It is impossible to train in Karate without encountering pain at some point. Pain may come in the form of sore muscles, getting winded, being punched, or muscle strain during a long, low squat. We must train our mind to overcome these small physical inconveniences. I remember years ago, when students would rub the ridges of old fashioned glass Coke bottles up and down their shins, just to toughen them. This might sound a little extremist for today, but I just use it as an example. The following quote is from Moving Zen by C.W. Nicol, and it relates to pain.

"Karate training had also helped me to bear pain. Perhaps "bear" is not the right word. "Bearing" implies a stoical indifference, a gritting of the teeth, a special courage. No. I had begun to learn to "see" pain, to recognize it, to know it, to realize its value as a warning signal, and then to override it if I so wished. A shin is bruised badly, but the match is not finished. The mind sees the injury and appreciates it for what it truly is-a signal from one part of the body- not a total destruction of psyche. My teacher, Kanazawa, had won the All Japan Karate championships with a broken arm. However, this total disassociation from pain would be very dangerous, and the Karateka does not do this."

Arigato, Ed Hall  - Titusville Karate Club.