When I first studied Wing Chun, I had no idea what principles meant or how they related to fighting. My fighting was very instinctive. I won mostly by out-speeding my opponent, not recognizing that I had many holes in my defense. Once I understood principles, my Wing Chun fighting improved dramatically. I now fight with principles in mind, which makes my fighting more economical in movement and also requires less energy.
The idea of using principles first dawned on me while I was designing a woman's self defense course based on Wing Chun. These principles helped the women in the course to have a fighting chance. From my own experience, these principles also helped me in my Wing Chun fights. Before, when I fought with very stiff males, I used to struggle against that hardness. I realized how ridiculous that was. Because of my understanding of the idea of soft against hard, I now just let that hardness be hard, and I just crawl on top. I visualized the situation like a cat walking on top of a wall; me being the cat and the hardness being the wall. So instead of pounding, trying to break the wall, just walk over the wall.
When some of my students encounter stiff controlling arms, they immediately struggle to break loose. They want to break away from that force. Instead of trying that, I advise them to think of other ways. For example, go over the hand, go under it, sneak through it. Act like as if you were a slippery snake. These are all principles of Wing Chun.
With strong people, I have to change quickly so that the opponent can't grab me. In sticking hands, strong opponent's often try to grab. To realistically stop a grab, I have no alternative but to hit my opponent hard with my elbow or anything else that I have free.
Principles can definitely improve anyone's fighting. Even just thinking about the principles can make a significant difference to your Wing Chun. Physical training alone, without the brainwork, is just not enough!
The Wing Chun Kung Fu Digital Library