It’s very simple: The tactical priority in self-defense is the preservation of self.
Out of all the possible threats to the self, the self is by far the most likely assailant.
As such, a true self-defense system would address this fact and would thereby include problematizing all the ways we contribute to our own unwellness - that is all the ways we contribute to our mental illness, to our physical illness, to our unhealthy social relationships, and to any and all of our at-risk behaviors.
The idea of a practitioner that spars well under a kick-boxing rule set or an MMA rule set but that suffers from anxiety or depression, and/or that is socially alienating, and/or that self-medicates legally or illegally, is good at self-defense is actually not true: Such a person actually sucks at self-defense. Yet, how many self-defense schools do we see that actually address this, the most common threat? Nearly none. Most, in practice, actually contribute to such unwellness.
Next, but far down in tactical possibility from the former, a lot lower than the marketing campaigns of the self-defense industry would mislead us to believe, are threats from others. In these cases, following sound strategy, one should prioritize anti-exposure tactics as the number one self-defense solution. In this case, more than anything else, this means practicing healthy and socially-established/supported lifestyles. This means building healthy relationships with others, getting an education, starting a career, getting married, having a family, learning to be polite and socially supportive of all people, having good communication skills, etc. In this, the cultivation of a sound lifestyle, when combined with the former, the problematizing of all the ways we attack ourselves, one pretty much has taken care of every possible threat one is likely to face in reality. Yet, again, how many “self-defense” schools do you see actually addressing these things? Nearly none. Again, instead, in practice, most actually support, either directly or indirectly, socially unsound lifestyles.
Next come the more rare cases, cases wherein we are attacked by others but wherein our anti-exposure tactics did not or could not function as intended. Here, long before employing physical tactical architectures, a mistake the self-defense industry always proposes, one should utilize battlefield strategies designed to increase advantage. These would include at a minimum means of gaining terrain advantage (both for assault and for extraction), means of gaining numerical advantage, means of gain an arsenal advantage, and means of controlling for tempo. Supporting strategies would then be employed, and these would be aimed at generating deception and at generating a sound legal defense. The gaining of such advantage has a de-escalating effect on assailants and the most tactically savvy of them will actually be deterred from assaulting you. Again, how many “self-defense” school address these things? Nearly none. In fact, most are 100% totally ignorant of basic battlefield strategic theory, and most actually propose, again either directly or indirectly, unsound legal defense strategies. Most are going to in the assault and then get people locked up and in court.
Last, come the extremely rare cases wherein an other-assailant persists through these strategies and tactics, being not deterred by them. In this case, the greatest self-defense art one can employ is an integrated weapon/empty-hand system, one based in non-contestation tactics. For weapons, at a minimum, this would include knives, clubs, and handguns. And, since weapons are involved, it would also include "stop the bleeding" wound care. Meaning, your everyday carry would at a minimum have you armed with two knives, one handgun, one spare magazine, and a tourniquet. Any "self-defense" school proposing contesting tactics and/or empty-hand tactics IS NOT teaching you real self-defense. They are selling you a product, and they are using misleading marketing strategies to do it. It is exactly the same for those "self-defense" schools that do not first address your own unwellness, your own unsound lifestyle, and your ignorance on battlefield strategy theory: They are not teaching you real self-defense. They are selling you something, something that preys on your egoic mind's tendency to generate a fantasy narrative for your life, one wherein you can act upon your unreconciled will to power, one in which you are the hero - in duplication of Hollywood's preying upon us - one wherein you are the mark in another one of modernity's Limbic Capitalist marketing schemes.