movement

This may sound overly simple: if you can't move, you can't fight.
Physcial confrontations usually require movement. They throw a punch or jump on you in some way, you act in response to their move, or before that you take intiative and get them first.
Therefore, I feel that you need to be able to move. We practice this through the use of langkah, or lower body meta-movements.
These are basically footwork patterns that one can use as is or in combination with upper body meta-movements called djuru-djurus (or jurus for short).
The basic footwork is a straight line or garis. You move forward or back. Another form is tiga or triangle stepping. These are usually at a 45-degree angle but not necessarily.
How you move your feet will dictate what your upper body does, so one needs to be aware of positioning.
There are also various ways to move your feet. You can step and then bring the other foot along, you can push with the front or rear to move forward or away from the opponent. Another close range use of the feet is to rapidly replace one for the other in a pendulum-like fashion. This is excellent for close kicks or rapid retreats.
There are variations of a theme for the above and some stylistic versions as well.
Do your footwork!
Jay