....without really thinking it through? Or alternatively, knowing full well it wasn't going to work out, but doing it anyway?
I guess I should go first. There are probably loads, but these spring to mind:
1 - I was at a large country park or zoo with my DCs when they were little (I forget exactly where). I plucked up the courage to go on one of those vertical drop 'death' slides, but as I was about to start sliding, I changed my mind, tried to grab on to the bar at the top, but it was fractionally too late. Gravity was clearly working against me, and I ended up with a very sore shoulder. I was lucky not to wrench it out of its socket completely.
2 - Much more recently, I was explaining to someone else's DC about the Natural Law Party and yogic flying. The child had never heard of it, so I pulled my legs into the Lotus position to demonstrate. There was a VERY loud crack, followed by excruciating pain as my kneecap dislocated.
A couple of weeks later, when I had mostly recovered, somebody else asked me how I'd dislocated my knee. I showed them how I did it... dislocating it again in the process!
I'm a competent adult most of the time, I swear! But I'm also one of those people with various degrees and loads of other qualifications, and zero common sense. 😂