I'm reading the book On Killing by Lt. Col. Dave Grossman. It's a book about psychology and warfare, and it has much to say about soldiers in combat, and the general human resistance to killing another human. It's kind of an interesting read, although he consistently claims that "the vast majority" of combat veterans eventually lapse into insanity, which I think is a bit sensational, and probably slanted just a bit. Anyway, in the book, he quotes Jeff Cooper, and there's a pretty good takeaway there about the proper mindset for anybody who practices or intends to use their firearms for defense of themselves or others:
Any study of the atrocity list of recent years -- Starkweather, Speck, Manson, Richard Hickok, and Cary Smith, et al -- shows immediately that the victims, by their appalling ineptitude and timidity, virtually assisted in their own murders...
Any man who is a man may not, in honor, submit to threats of violence. But many men who are not cowards are simply unprepared for the fact of human savagery. They have not thought about it (incredible as this may appear to anyone who reads the papers or listens to the news) and they just don't know what to do. When they look right into the face of depravity or violence they are astonished and confounded.
Good point, Mr. Cooper. I shall endeavor to be prepared for the fact of human savagery, so that I may act quickly and decisively to defend myself and my family.