Some martial artists seek to be as fierce as an animal by copying the perceived behaviour of the beast.
Their emotions run wild, they lose control and become very aggressive.
This is not what we want in kung fu.

The kung fu person is not angry or aggressive; they are only doing what needs to be done.
Inwardly, the emotions are cool and relaxed, the mind quiet and expansive.
Their bearing suggests detachment combined with a physical readiness to act.