Being physically tired/fatigued is only one kind of stress. Also, when your body dumps a bunch of adrenaline, it won't be exactly the kind of stress you're going to be dealing with. I'm not saying it's not useful to try shooting fatigued, but there are other ways you can create stress.
Shoot with a friend, and put some money on who does better. Not necessarily a lot of money, but enough that you don't want to loose.
Or if you don't have a friend to shoot with you can agree to pay yourself for every good shot and charge yourself for every bad shot. And, the money you walk away with is all you can spend on beer for the week
It's amazing how much harder it is when something's actually riding on it.