At its core, Kung Fu and Tai Qi are about movement - and movement is Yin (陰) and Yang (陽). Instead of thinking about the power, strength and speed of your form think about the movement - the 陰 and 陽 of each action. This is where your form really lives.
Something else to think about...You are 陰 and 陽. A living, breathing, thinking, moving being. 陰) and 陽. Mental/ physical, inside/outside, front/back, top/bottom. Every thought, impluse and action is 陰 and 陽. The interaction of you and your surroundings results in a thought; the interaction of your brain and your body results in an impulse to move; and the interactions of your brain and your muscles, tendons etc. results in the actual movement. Your form is 陰 and 陽. Whether it is Kung Fu or Tai Qi, your form is a highly structured set of coordinated movements - 陰 and 陽. Your interaction with the form is another level of 陰 and 陽. So, you (and the form) are moving, spinning, turning and changing - experiencing and expressing 陰 and 陽. The result is alive with a personality, shape, flow, pace, and purpose.