Once when I was little, my parents had to go out of town and so they left our dachshund Fritz with my dad's brother Randy. During that time, Fritz got out and ran down the street and got nicked by a passing car. He wasn't seriously hurt, but my dad remembered it from that day on. Any time I wanted to spend time with my cousins years later, my dad would say, "Randy couldn't take care of Fritz, so he can't take care of my kids." OK. I do see that reasoning. (Years later when my dad was undergoing military psychiatric counseling, he wouldn't admit to being mean to his wife or kids, but WOULD say he was sorry for getting drunk and being mean to Fritz!)
When I was on my own, 20 or so, I never wanted a pet, because I'd never had a pet as an adult before and thought I was so angry I'd just be mean to it. My friend Kristine came across a Humane Society black cat who'd had 9 or 10 kittens. We lied and said the mama-cat was ours, and took all of the kittens home. They would have all been put to death if not for Kris. The runt of that litter, "Mr. Crusty" (because of the constant boogers around her eyes), turned out to be a girl-kitty that no-one wanted after everyone came and claimed the other kitties, and so she was mine. I renamed her "Frances." There was no way that I would have ever been mean to her. And since then I've never been scared of having pets.