Deterrence is the point at which Situational Awareness and defensive tactics come together.
Deterrence is the process of communicating to a threat, that you will not be a victim and that the risk in dealing with you is way more than the reward they might get in committing their crime. Deterrence has both physical and verbal actions that exist on a "use of force" continuum. From simply closing the line of communication to the threat - to bringing the full weight of the firearm to bare on the situation.
The thing with Deterrence is that you must practice. If you don't lay down the neural pathways for both verbal and physical actions, you won't have anything useful come out when you go under a Physiological Response to Stress.
It's hard to practice Deterrence in Live Fire, but it works great to practice it in Dry Fire.
Check it out.
Also, you can find the full lesson on Deterrence in the Concealed Carry Masters Course, available here.