Here is a true story: A Vietnam War veteran went to a self-defense class to support his girlfriend. She was told to be vigilant, always. She was told to be aware of her surroundings, always. She was told to hold her keys between her fingers like a weapon, to be prepared at all times for an attack, to treat every stranger like a potential enemy, a potential threat. Her boyfriend — a soldier, a vet — said it reminded him of his war training. War training is how I walk home from the subway after dark.