A colleague of mine in a previous life noted, in his annual review, that he constantly learned the same lesson of not over-committing. Forgive me for the obvious, but he didn't learn the lesson. You haven't learned the lesson until you eliminate the mistake. As far as I know he's still in the same job and still over-committing and still writing the same thing on his annual review which isn't worth the paper it's written on if it's been going on for as many years as it has.
But I loved the story the other day of the Pacific 'island' that was found not to exist. Sandy Island has been on maps for many years but when Aussie explorers went to check it out for a new mapping exercise it wasn't there. Seems that someone made a mistake and it got repeated ad infinitum.
From time to time I find myself repeating things I have been told without weighting them. I said something the other day and realised that I had never checked the alleged facts, just believed the bishop who told me them. I am a bit of a maven (Malcolm Gladwell word - person who tells a lot of others of his good experiences). If I am not careful I spread lies and misinformation.
Memo to self. Remember not to repeat 'facts' parrot fashion until you are sure they are right. I have to learn this over and over again. Oops.