I was about 15, and I got my period about a week early in bright white jods in the middle of the class. I felt it happening before I went into the ring but was focused on my horse and so dismissed it as nerves or something. There was nothing I could do once I felt myself start to leak.
It was a jumping class, so my butt was pushed out and visible.
As soon as I was done, I'd qualified for the jump off, but I loaded up with my jacket tied around my waist and got out of there.
Worse yet, my Dad was the only person with me, and I was 15, at that age I didn't talk about things like that with my Dad.
Everything is horrifying when you are 15, but this was especially so.