I was wrong
In 1993, I saw the web coming. I was hired to write the cover story for a now defunct computer magazine about the internet, and dismissed the new Mosaic browser in a single paragraph.
I figured the web was just like Prodigy, but slower, harder to use and without a business model.
About as expensive a wrong analysis as a single entrepreneur with an email company could make in 1993.
The reason it was an insanely valuable lesson: I got better at announcing that I was wrong, learning from it and doing the next thing.
Politicians, of course, are terrible at this. They are never wrong, apparently, and when they are, spin instead of admitting it. Which not only hurts their trustworthiness, it prevents them from learning anything.
Two elements of successful leadership: a willingness to be wrong and an eagerness to admit it.