Imagine somebody angrily swinging an iron pipe full speed at your head. What would you do? That depends on what kind of martial art that you have been taught. If you are a student of the traditional technique-based striking style martial art through repeated conditioning you would probably block the attack with your hand and counter-attack with the other hand or legs. This type of learned reaction will probably get you killed. The sensible thing to do is to step aside, not much but enough to let the weapon graze you, and counter attack with whatever is appropriate at the point in time. By not learning techniques and relying on your natural survival instinct your mind is free to invent it’s next move on the fly, because your brain has learned body mechanics through training, not martial forms cast in stone.
Relaxation response in a fight will enable you to take and survive hard blows. For example drunk drivers seldom get killed in the accidents they cause, because due to being drunk they are loose and relaxed. Even under extreme combat stress a free-style martial artist knows how to relax different parts of the body independently from each other and to use selective tension and relaxation to confuse or hurt an attacker. Contrast this with technique-centric martial art styles that condition the practitioner to tense his body by holding the breath as he meets the attack forcefully head on during sparring.
Natural and relaxed movements that are circular and curved will keep you out of harms way in an assualt situation better than the linear movements of the form based martial arts styles. Natural movements by their nature are not static but ever changing and dynamic evolving and responding to threats in the moment and each moment is different from the previous. Let's look at how a forms based martial art practitioner would react when a fist flies at his face. The natural reflex is to bend backwards while raising his hands to block the attack, leaving his feet right where they were. The problem whith this approach is that you're still in the line of attack, and a slight push will make you topple over, not to mention that you could trip on something behind you. Once you can reasonably move in a relaxed manner, a flurry of opportunities "magically" appear for you to take advantage of. Your brain, free of unreasonable fear, has learned to recognize those opportunities and make your body move as to steal your opponent’s movement and make it yours, to his demise.
Breathing in through the nose and out through the mouth naturally and freely is essential to absorb blows, combat stress and also inflict damage to your attacker in a fight. Everyone breathes, we have been since the day of our birth. Breathing naturally and freely might sound simple enough yet in some traditional martial art tournaments that I see the practitioners tend to hold their breath at some point in time or restrict their breaths in response to combat stress and tension. Our strength comes not only from the food that we eat but also oxygen in the atmosphere. Forget to breathe for a few seconds, due to oxygen depletion in your lungs and you will run into a world of trouble fifteen or twenty seconds later, even after resuming it. For not breathing and regulating the oxygen intake some competitors even find 2-minute full contact rounds too exhausting to continue beyond.
You require a good posture in order to move around freely, naturally and in a relaxed manner. Good posture does not imply a myriad of complicated body forms that mimic certain animal postures that you see in some traditional martial art styles. Simply stated, good posture should be as simple and practical as keeping your back straight as much as possible all the time. If you need to go down, bend your knees, not your back. If you need to move forward, backward, sideways or turning move your legs but always keeping your back plumb.
Stepping aside, relaxation, movement, breathing and good posture are not specific techniques but general martial principles derived from your natural and instinctive response that will ensure your survival in a confrontation. By not forcing learned techniques to deal with ever changing modes of attack and relying on the 5 principles you will gain the freedom to use all parts of your body (shoulder, knee, leg, forearm, head, finger, elbow, etc) to strike. For example with freedom from the limitations of conforming to techniques your blows will tend to be loose and heavy, like hitting with a sledge hammer on a string. Your response to attacks will not only be multi-dimensional but also multi-directional, and used to maximum effect to negate your attack's form and balance.
This is not to deny that the traditional technique based martial arts training in the dojo that you receive from your sensei has no role to play. Training in the traditional styles in the dojo can be used as a basis for developing strong martial fundamentals eg posture, centering, grounding, concentration, power, speed, combat distance, agility, discipline, different types of attack and defence forms, weapons, break falls, etc mastery of all of these fundamental skills will surely enhance your attack and defence capability in the development of formless martial art. For many people it is difficult to learn any thing without some sort of structure and free fighting has no structure. Thus practicing traditional technique style martial art with its focus on rigid structures can be seen as a necessary prerequisite, a sort of DNA for further progress to the next level of no form martial development.
Just be aware that in case when you are forced to resolve a showdown outside the comfort zone of the dojo environment eg in the streets, you may have to adapt the basic skills and fundamentals that you learn in the dojo to survive the attack as the technique-based and structured traditional style martial art training that you receive may not get you out of serious trouble.