If you're looking to cultivate high level skills in Kung Fu, Brazilian Jiu Jitsu, Karate, Judo, or whatever practice, there are four essential areas that you must train in.
Ignore one, and the others suffer.
Your training must incorporate all four if you want to have the best chances possible of training for long-term health.
Unfortunately, most of these have a lot of mystical claptrap associated with them, and it can be difficult to separate the good from the bad.
That's why we have the twin tools of logic & reason to help us out.
1. Chi Gung
Often thought of as simply breath work, it's a bigger concept than that. Chi Gung is not just different breathing patterns; it's also overall cardiovascular health and condition.
Essentially, how big is your gas tank? All things being equal, the fighter with the more efficient/well developed oxygen/CO2 system is going to win.
2. Chi Sau
Often called "Sticky Hands," and practiced as a partnered drill (both structured & not), it's essentially the practice of cultivating greater sensitivity to the intention of your opponent.
There's an idea in psychology called "Liminality" which is the level that a stimulus has to reach before you're consciously aware of it. This is where the idea "sub-liminal" advertising comes from: your senses notice the input, but you're not consciously aware of its influence.
Sensitivity practice effectively reduce the liminal threshold making you more perceptive to someone's intent. You learn to hear more with less.
3. Chi Gerk
If Chi Sau is 'Sticky Hands,' Chi Gerk is 'Sticky Legs' basically meaning footwork. This is an awareness of the importance of distance management, positioning, and attacking an opponent's base of operations.
No matter how good someone's striking is, it means nothing if there legs are taken out from under them.
This a broad practice, but it's importance cannot be overstated. This is the foundation that all other techniques are built on.
Balance, movement, and connection with the earth.
4. Chi Na
The art of grasping and seizing; joint locks and grappling.
In close quarters you're often going to have opportunity to tie up the limbs of your opponent, or break bones, dislocate joints, or any number of devastating applications of the Chi Na principles.
It's nasty business, but if you're in a situation that needs it, you'd be well served to be well-versed in it.
These are the four essential elements of your self defense (and life long wellness training).
Know how to breathe, perceive, move, and make & break connections.
Fight hard, train harder.