Let’s face it–we’re not as smart as we think we are.
When you take a closer look at, say, the mistake that made you lose a chess game, you marvel at its sheer stupidity. Of course you knew better than to make that stupid move! And you can list the reasons why. Ah, but you made it anyway.
Now imagine you’re directing foreign policy or micro-managing the course of human evolution, blah-blah, and you make a stupid mistake that costs billions of dollars and starts a war…
It happens all the time. We call it history.