You never know when a stranger will press an attache case into your hands at an airport seconds before a gunfight will break out. You never know when the next door neighbor will knock at your apartment door and beg for help because pistol-wielding assassins are climbing in her window. One day, without warning, a man in a black suit and aviator sunglasses will take you aside and tell you your country needs you, and then whisk you into an underground bunker or a ready submarine.
You must be prepared for that moment. You must get your body in shape. You must learn how to drive a motorcycle, fire a pistol, dress a wound, encrypt a file, and leap from the top floor of a building into a dumpster. You must train yourself to run five miles at a dead heat. You must speak several languages. You must be able to pick a lock.
Start now. Teach yourself how to find out anything about anybody. Learn to tail someone so that they do not notice. Put together your go bag. Learn a martial art. Learn several.
This is your textbook. Some of it will seem unnecessary. Some will seem silly. Learn it all. You must be a spy waiting to happen. When the room explodes into chaos, when the fists and bullets fly, when the handgun skitters across the floor and lands at your feet, you must be ready to pick it up and go into action. You must be a danger man.