In Karate through many generations, the wisdom and the tools were developed and transmitted to achieve harmony in oneself and with opponent.
Those are not beautiful theories only, in karate harmony within oneself and than with the opponent is a necessity. You will get an immediate feedback when facing a good opponent, if you are not "present", and not in harmony.
This harmony has to be there not only when you lie down on the beach, but when you are on the edge, at extreme situations.
Mind in karate refers to as heart, feeling, intuitive mind.
Harmony in your body means that your body coordinates and integrates, moves in optimal sequences to produce maximum force with least effort, and it instantly follows your intentions.
Achieving this level is a long, unending journey, I will describe some of the tools we use.
My teacher, Sensei Nishiyama, used to shout at me "don't use eyes", "bypass the brain", and he did not mean that in karate we learn to be stupid and do not use our brains.
It means that in karate we strive to achieve balance between brain and mind (heart), conscious and intuition.
We make strategies with our brain, we have to be smarter than the opponent, but when the interaction with opponent began there is too much information and too little time for the conscious brain to handle, and then our knowledge, decisions and actions have to come from somewhere else, we have to tap into a different kind of knowledge.
Our intuitive mind and breath with our previous experiences together have to perceive the opponent, and carry out our actions.
How do we do that?
We start by teaching the body to be most effective, moving out of optimal posture, from the ground up, with the the body center as action center and intention center, we don't have arm or leg movement in isolation, even if one finger moves the whole body cooperates.
Step by step we learn to control all phases of technique with the breath to the point that there is no thought of details, there is only intention and breath, the breath is the "trigger" that initiates our action, and also controls the the type of energy in each action, smooth, continuous, sharp shock.
At the next level, we learn to "catch" the opponent's rhythm and action with our breath, our breathing tunes to the opponent's breath while our eyes observe, monitor, but we do not judge, do not interfere.
We say "eyes way back" as if looking at a far mountain so the brain will not interfere, and than we can start seeing the cues and information that are beyond the external movement. We are looking to opponent's breathing, and moreover looking to opponent's heart (feeling, intention).
Now our breath controls our body action, and interacts, harmonizes with opponent's breath and rhythm, our breath initiate our action and our breath make the reaction, there is no need for judgement, confirming, which is delaying our movement and cause hesitation, doubt and unstable emotion, it also causes us to get stuck in what we see, in this or other detail, and it blocks are intuitive "antennas".
Breath reaction is a way to avoid over using the brain, allowing intuitive mind to turn on, and it allows us to give everything without interference of the conscious brain once we move.
being intuitive means to be sensitive and see all the cues and information that the opponent gives us without getting stuck on one detail or another. It is not some guess nor it is magic, it is being tuned and allows us to use tools that all of us have.
Breath reaction is not enough, it has to work with the previous experiences we accumulated, since with time we face many circumstances and know all the possibilities the opponent has, and also our nervous system is wired properly and we have the skills to handle any attack with ease.
So we have step by step tools to allow our mind, brain and body to work in unison, but , it is not a math formula, and takes a lot of trial and error, making mistakes and adjusting.
Wayne Gretzki, the hockey great, had it, that is why he could be the best hockey player ever without being the most athletic. But only in karate we have systematic method that allow any person to achieve those levels.
In karate we say "think by mind (heart), act by ki (mental energy from body center)", we say "you don't see (with eyes) yet you see (with heart), you don't hear yet you hear, you don't know (with brain) yet you know (with subconscious mind)". and everyone can achieve this level of awareness and intuition with proper training and dedication.