When I was much younger I did an experiment of intention.
I cleared my mind prior to lifting a full, multi-litre water jug and imagined the object to be extremely heavy as if full of concrete. Grunting, I lifted it with my weak arm a few inches off the ground.
I, then, cleared my mind again, and thought of the jug as being empty. With the same arm, I lifted the container up to my waist with ease.
Another experiment is the following: Sitting in a chair, slow your breathing until you are very relaxed. Go through each part of your body, from your toes to your eyelids, consciously telling each and every muscle to loosen and unwind. Breathe more.... even slower. After several minutes, imagine two helium balloons attached to each wrist, and ever-so-slowly, as you breathe, visualize the balloons slowly rising into the air, inch by inch. The process will take several minutes, if done correctly, but by the end you will find your arms have been raised up over your head without any direct signals from your ego-brain.
You have just hypnotized yourself.
Now, on a heavy bag, imagine the target is soft and that your leg is full of qi energy. Loosen your muscles and unhinge the joints so you can visualize the energy move like a whip.
Regardless of why, or how, it will somehow feel better.... stronger..... and easier.
Now, have you just hypnotized yourself, or have you just allowed your energy to behave how it really is?