Your first consideration is reality. We have to accept the concept we must prevent being in a situation requiring self-defense. Someone we work with, family member, neighbors, friend, spouse, etc. It is seldom a gang-banger, stranger type of person. We sometimes fear the unknowns out there more than those around us.
Tempers can flare over matters such as money, property lines, emotions and more.
Those areas are ripe for a disaster. The reason for that is that you failed to back-off or get out of the situation. People have been killed in disputes for things as trivial as a parking place. When tempers flare you step beyond the area that is self-defense and you can become the antagonist and the predator. Self-defense in almost every case will demand you show what you did to avoid the problem.