When I was about 11 years old, my best friend and I were playing during recess at school, and I was carrying him around on my back, presumably pretending to be a multipart attack robot. All of a sudden, my heart started hurting, and I collapsed to my knees, and the robot was no more. Every time I inhaled, it would feel like a spike was being driven into my heart, and my breathing got completely shallow. I was sure I was done for, when all of a sudden, after an exhale, it disappeared.
It wasn't until I was in my twenties that I learned this was called Precordial catch syndrome and it happens to most everyone. Every friend I've told about it was surprised, and also most knew the feeling.
I collected a growing list of strange things bodies do ever since. And now finally I made it into a little page for others to see:
https://vester.si/bodily-oddities/
It includes a form to tell me about new things, if you think they belong on the page. Feedback welcome!
I wish I had kept a notebook of this stuff as a kid, I remember having a lot of odd experiences and sharing them with my friends, but it was so long ago now.
I think most of them were visual oddities.
I remember seeing floaters for the first time, and asking my mother about them.
"Oh, that's just [neighbor] throwing trash out the window."
The delights of growing up in Eastern Europe!
I also get these "worms", bright glowing white. I heard they might be white blood cells moving through capillaries, but why would they be glowing? I usually see them after cardio.
Another fun thing to do is to stare at one point until your entire visual field goes grey (the afterimage cancels out the image... "neurons get tired" or something), then slightly move back/forward or slightly rotate your head, producing very interesting patterns from the interference...
I should write a book...