Why do I wet myself when I get beat?

One time I got beat and I piss myself at age 8. It made me felt humiliated and powerless, another time I was 13 this guy hit my knee and I felt a little pee came out and luckily I could control it and my eyes start watering and he saw and was watching me I was embarrassed. Maybe it has to do with fear or pain I don't know ๐Ÿ˜•
Why do I wet myself when I get beat?
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