Reimian Empire

Wait. Let's use a revolver as an example. I have one bullet. I spin the cylinder, then shoot myself in the head. I don't die. I spin the cylinder again, shoot myself in the head again, and still don't die. What prevents me from spinning the cylinder and shooting myself for the rest of my life without ever actually dying? What's wrong with my example?

Yes, everything is as you said. A twenty-round revolver with one bullet.
In principle, nothing prevents you from surviving until you die a natural death.
Let's calculate: suppose you have 10 years left to live, and you can shoot (taking into account breaks for sleep, food, finding bullets, etc.) once a day.
That is, even assuming that there are no more than 365 days in a year, you have 3650 attempts to die. Each time, you need the cylinder to be empty, and there are 19 empty chambers out of 20.
0.95^3650 = 5 * 10^-82. That is, the chances of surviving are not just small. They are very small. It's like the chance of finding a specific water molecule in 63 liters of water.