Remember that a person can stop your motion, jam you up and off-balance you only if he has a direct line with his pressure to your center of gravity, no matter where he's pushing from or through.
If he can never find your center of gravity, he can never stop your motion, jam you up or off-balance you.
One way to lessen his ability to find your center of gravity is to keep it constantly moving--which you should usually do anyway in the name of body unity.
Let’s talk about “center of gravity” in this context as the point on the ground coinciding with the plumb line that falls from your physical center of gravity within your lower torso. We keep it constantly moving by pressing our feet against the ground such that the position of that point on the ground keeps changing relative to where our feet are on the ground. This can apply even if you are on one foot, as there are infinite points on the ground within the span of your foot on which that plumb line can fall, and infinite points on the bottom of that foot with which to push against the ground to shift that plumb line’s position. If you have two feet on the ground, of course, that range of possible “center of gravity points” greatly expands, but remember the ideal is to move things as subtly as possible, not as much as possible.
Here, try to push me off-balance. So long as I keep my center of gravity moving, I’ll be okay, and your attempts to push against my center of gravity will fail and slide harmlessly off my body as my center of gravity continues to subtly move, such that when you think you have a bead on it, it’s already moved somewhere else.
HOWEVER, people frequently mess this up due to allowing their conscious minds to fixate somewhere. Let’s say this time, when you go to push me off-balance, you do it a little more suddenly and violently, such that my mind registers the contact as a threat or something to worry about. As my mind fixates on that threat, my center of gravity stops moving and becomes vulnerable. Often I’ll also do something stiff, spastic, overcommitted and disunited in an attempt to evade or escape the perceived threat. That combination of catastrophes will spell my doom.
Hence we see that our survival in this case comes down to our ability to control our mind, or to not allow our conscious mind to control us.
The idea I drilled with my students was as follows:
No matter what happens, as we flow, concentrate only on the feeling of the feet pressing against the ground, ensuring constant change, ergo constant movement of the center of gravity, creating a Root That Can’t Be Found. Consciously ignore anything else that is going on, simply stay in contact and allow your body to move with everything while keeping your head suspended from a string (i.e. neutral, relaxed posture with no leaning). Focus on and visualize only the bottoms of your feet against the floor, feeling every tiny change as precisely as possible.
As long as you are able to maintain that mental focus, notice that nothing bad happens to you! Attempts to push you off balance slide harmlessly off your body. Attempted strikes drift harmlessly past you, as your moving center of gravity moves your head and body above it as well.
But notice what happens the instant you allow your mind to shift to what I may be doing to you:
You mentally register my attempt to push you, and rather than allowing your center of gravity to continue to move and obviate the potential problem with no effort, that movement STOPS as you focus on the hand on your body. Your body may attempt to pocket or twist out of the way, your hand my try to push my hand away, but because your mind became fixated, your center of gravity became stationary, your root is found, and all excess efforts are for naught.
Keeping your mind in the bottoms of your feet, you can move in, cutting off my movement and ability to stay on balance. Even as you step forward, you are not COMMITTED forward. Just as in the balance exercises, you place your foot and shift your center of gravity, keeping it free and movable in any direction at any time. Remember that feet cannot move any faster than the hands and the rest of the body.
Remember that the idea of keeping the mind focused on the bottoms of your feet is just a trick to prevent the as-yet-untrained mind from fixating on anything else. Eventually you want to train your mind to observe everything and fixate on nothing, staying open and present while freeing the subconscious to do what it does best, without having to resort to tricks or devices.
Generalizing from here, if you can keep your mind fluid, you can keep your body fluid, and have little to fear. As soon as your mind fixates, you are screwed. The better you can maintain this mental and physical fluidity under increasing amounts of pressure (speed/power/danger), the greater your mastery of Guided Chaos and the greater your potential combat effectiveness.
Spoiler alert: A moving center of gravity can still be found and taken advantage of by someone with a higher level of sensitivity. We then must get into deceptiveness, masking the movement of the center of gravity behind false surfaces and equal pressure, etc. LOTS more levels to this stuff!