Excessive speed on a bicycle. Alright, I did it more than once, until a slow car scared the shit out of me.
At one point I lived near a small mountain with a road going up. It was so slow and painful to get up, but a huge thrill going down. I didn’t have a speedometer but it was a 45mph road (and everyone speeds) and I consistently passed cars. It had only one lane in each direction and I regularly passed cars going over 45 mph, by a lot. Then one day I was about to pass the car and she slowed to turn. Panic time, huge continual squeal of my brakes that scared her into accelerating past her turn, and I still zoomed by on the shoulder before I could stop, hundreds of feet beyond.
Clearly way too fast for my vehicle and my (lack of) protective gear
It's so much fun to dive-bomb down a mountain road, but as soon as you get a little rain, a little shimmy develops in your front steering column that cascades into being thrown over the handlebars... I've had a few close calls, where during a race and during a regular ride, where I almost ate shit hard... Yeah, I'll just slow down a bit sooner next time 😳
Had a tamer but similar hill near my home growing up. Loved speeding down. It ended in a lot filled with gravel. Fortunately the day I spun out on the gravel lot was coming from a different, slower direction. Developed an extremely bad case of road rash all over one leg. When I realized what might have happened if I'd been taking the hill instead, that I probably would have broken my legs or worse, I stopped going down that hill. Realization of mortality can be like a bucket of ice water sometimes.