From a lecture by Col. David Grossman, which I have never forgotten. He is speaking about not being armed and prepared, which he calls denial.
"Denial kills you twice. It kills you once, at your moment of truth when you are not physically prepared: you didn't bring your gun, you didn't train. Your only defense was wishful thinking. Hope is not a strategy. Denial kills you a second time because even if you do physically survive, you are psychologically shattered by your fear helplessness and horror at your moment of truth."