He's proposing this as a test, not as a recipe. He's not saying "do what you'd do if this day was your last," but rather "consider what you're about to do, and

He's proposing this as a test, not as a recipe. He's not saying "do what you'd do if this day was your last," but rather "consider what you're about to do, and measure how close it is to what you'd do if this day were your last."