I once watched my instructor fight two younger black belts who were testing for rank. The cocky 20 year old black belts were good and were making other students look bad, so the head judge sent my instructor in to fight them. It was similar to watching a cat play with a mouse. The cat catches the mouse and keeps letting him go. The mouse feels he has a chance to escape each time, but at some point the cat tires of the game and eats the mouse.
When the black belts fought my instructor, they threw every technique in their arsenal and thought that since they were so active that they must be winning. However, at some point, you could see the desperation on their faces when they realized that none of their techniques were getting in and that my instructor’s techniques were not only getting in but were purposefully being reduced in speed and power. He was just relaxing and playing with them. Then, after the instructor had finished teaching them a lesson, he picked them apart with a flurry perfectly focused techniques that completely demoralized the fighters. He was not as young, not as quick, could not kick as high, and was not as fit as the black belts were, but he was a master at the art of Taekwondo.