First know yourself before attempting to know others.Unlike the first three, this one doesn't have an obvious connection to the martial arts. What does "knowing yourself" have to do with karate?
People who have studied the martial arts - or any other demanding discipline - seriously for a time know, however, that any discipline in a journey of self-knowledge. In the case of karate, the more I study and practice the more I learn about myself physically, mentally, and emotionally. I learn what I can and can't do, what I am and am not prepared to do, what my strengths and limitations are, and how far I can push the boundaries of all of these things.
The injunction to know yourself before trying to know others starts with the physical. If I don't understand my own body and its movements, someone else's will likely baffle me. That's why people with expertise in any area, from sports to martial arts to music, can watch someone else perform and "see" things that the rest of us can't see.
But this pretty quickly goes beyond the physical. If I haven't made the effort to understand myself, to get "inside" something and try to make it work for me, how can I pass judgment on someone else? And if I haven't really wrestled with myself in a given area, to test my ideas and thoughts and values, how then can I try to do so with someone else?
At its heart, this is a call for humility. It is entirely consistent with the parable about specks and logs (Matthew 7), and any number of other teachings about the need to understand ourselves rather than pass judgment on others.
In this day and age, humility is not much commended as a virtue anymore. We are quick to pass judgment on others, to rain down our wrath and indignation on things we don't understand. Trying to understand, rather than to judge, is seen as weak. For a recent example, check out this story about reactions to a staff member at Ohio State who suggested (via Twitter) that a search for compassion and understanding were appropriate towards the perpetrator of violence.
In today's world, humility takes courage, because it means standing up to the mobs baying for blood. But as CS Lewis reminded us, courage is really the form of every virtue at the point where it is tested. Today we humility is facing terrible and difficult tests. Will you try to know yourself first?