What made Ba Gua unique from other martial arts was its continuous changing and the way that it made the
inside of the body like a morphing snake.  
The object was to turn the body into something that could morph the same way the movements of the
Universe morph, from a Taoistic perspective,
bringing the mind and the body together,
so that at a certain point if you could link with the forces of the universe, they could move you, or you
could move yourself,
until finally both things became in sync, at which point the mind/soul/spirit opens up and connects.  
And eventually if that goes far enough, you end up in the place where
all things are flowing through you and you are flowing through them -- this is what the
Taoists call "being one with nature."  
It means that your internal movements at every level are in direct sync with every other movement that occurs.
There are many methods in Ba Gua designed to cultivate stability of the mind, which is necessary
to enable you to manage stress
and fear.
Taoism predates Buddhism and is based on the principles described by Lao Tse, Chuang Tse, and the
I Ching over
2,500 years ago.