After years of kung fu and other martial arts I trained in the west i switched to muay thai. When i was doing wing chun i found repetition was the thing that stopped my brain from freaking out when in a stressful situation ,your body just starts to react by itself so no thought necessary if you have done the movement a billion times before. But i found that my techniques where sloppy and i was lacking serious power and speed when under stress when my mind starts running all over the place. First day I started training muay thai here in thailand i was taught two things that was more valuable to me than any of the techniques i have learned. Sabaai sabaai(chill chill) and Sanook( fun/enjoy). The trainer said i am too tense and i do not look like i am enjoying it. I knew i loved what i was doing but i wasn't smiling( just forcing yourself to smile when you are sparring or training has a interesting psychological effect on a person,try it.) in other words I have learned to push myself and try my best to hit as hard and fast as I can and to move as best i can an not give up which is great but you end up trying too hard. Now i train like i don't care how hard i hit. I don't think i just do it as best i can while still staying calm and relaxed. If I feel my body tense or I grit my teeth at any point I stop , breath, dance a little and start again not caring if its my best or worse kick , instead i just kick or punch. I am now hitting way harder and my mind doesn't fuddle nearly as much because there is no over thinking.I don't clench my mind anymore in order to go harder. I am relaxed , smiling and enjoying every minute of training. Many guys from the west have this problem with tension that come and train here. chilling out is kinda built into Thai culture. You only tense the muscles you need and not your whole body and the muscle that needs to be the most Sabaai of all....your mind. Like they say in kung fu the more tension you have in your body during a technique the less force has transferred to your opponent. Bruce lee says that you fight exactly the same way as you train so train as if every punch and kick is real and not just a sparring partner. True but that's why i have started training my techniques with the same mindset that I make a cup of coffee in the morning or walk to work. No thoughts. Just do it. If you need to adjust and improve it do so and then again just do it relaxed with no thoughts and smiling. Then if push comes to shove your body and mind will respond the same way you spar and train.Relaxed and fluid as opposed to kicking in your fight or flight response , tunnel vision and then all the martial arts gos out the window.I find in the west we get way too serious which causes our minds to tense even when we meditate and breath.We start to seriously meditate. Hope all of this is useful and makes sense. It helped me alot to just go with it a little more and have fun even if i am training really really hard. This is a fight between too top level fighters here. Notice unlike western fighters they arent wailing into each other with everything they have straight out. They are relaxed and waiting for a gap and you only see the tension for a split second the moment they take a gap.