Fa means to 'throw' in the sense of 'releasing a kite to the wind'. 'Jin' simply means 'Refined Force'. The question is, What is being refined? What is being thrown? This can be a productive metaphor upon which to dwell. Training progresses from big movement, to small movement, to 'no movement'. The tendons must become strong and supple. Relaxation must be present in order for beginners to 'sink the chi' and, later, for the bones to play their proper role in all movement at all times. Fajin is the natural product of this specific awareness.
Understanding the structure means to be able to agree with gravity. There are no shortcuts. To cultivate 'the energy' without a deep understanding of structure and relaxation, leads to 'artificial power'. Artificial power is easily defeated by natural power. This arises from the differences of the quality of the awareness produced by differing training approaches.
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