Working with permission and letting yourself be moved is not easy. We tend to tense up when we are pushed or hit to keep our place or where we think we should be in our mind. Try this: It is easy to move with a push in the side of the chest since we see the side hit and naturally rotate with it to avoid injury (espacially if we are training with a knife or any sharp thing) work with a friend and push each other using fists. Start from the side pushes and advance to the middle of the body so the whole revolving door idea of moving to avoid injury is not so clear anymore. Now sense in your body which side of the fist is pushing either first or stronger and give from that side. It involves relaxing your hips and legs mostly so you can turn inside the axis but don’t neglect the upper body and keep your form. Do it slowly to learn the difference between the sides of the fist in hitting and learn to place your fist so there is less movement on your friends side when you do hit. Another way to illustrate this would be to work with your back to the wall (no leaning) If you are pushed in the center of the body and have to give, than give where the push is stronger (sensitivity) and turn on your axis since there is back to turn to. Have the fist travel without changing at all if you can so it reaches the wall where you were and not to the side.