Then my friend asked us all whether we could remember situations when we'd been wrong. Being deep in the financial news that day, I replied with some pretty clear investment errors where I'd entirely missed a couple of equity booms because I'd believed they were irrational. I'd missed the ensuing bust, too, but that simply made it a wash--nothing to be particularly proud of there. It was when I learned the truth of Keynes' comment on market irrationality.
Thinking about it later, I realized that I had much better, and probably more interesting--at least to the intended audience--examples of my own error, but that my focus on finance at that moment kept them from occurring to me at the time. Errors which could be quantified in dollars and cents seemed more compelling.
I was entirely wrong, coming out of college, about some pretty fundamental things about life: How money and careers worked. My ideas about gender and dating. Conventional wisdom about current affairs.
These were mostly unexceptionally popular ideas, and the ones I assumed were true turned out largely to be wrong. I ended up making some big mistakes. It took decades to unlearn them, but at least the unlearning of them made me realize how wrong I could be. I could be deeply wrong about things I cared a great deal about, and that I simply took as axiomatically correct.
Learning that was helpful. I think it may have made me a more cautious investor but much more open to the possibilities of life in general. That was probably a good trade.