Wrong means = wrong end

The body, freed of tension, should reach a condition where the joints move freely.
Only then is the body loose enough for fa jing.
You must be sufficiently attuned to your own movements to feel when and how fa jing can be generated.

Some students are not patient enough and use force.
A common mistake is to use the pelvis and hips rather than the combined muscles of the entire body.
People become adept at rapid pelvic turns or abrupt shunts of force.
These are quite strong but they are not fa jing.
They tend to create a residual pattern of tension within the body.

Fa jing is like a wave, rippling up from the ground, through your hand and into the opponent.
Instead of using the hips and pelvis, you should use the spiralling of the legs, the opening and closing of the spine and the movement of the centre.