What perfectly normal thing can't you be around anymore due to something you experienced?
Mine is a pretty tame example: I never minded the smell of garlic was fine around it... but I took a job for DHL and they had these large tubs of garlic for horses that had to go out to people. There were about 10 of them coming down the belt.
Now I can't stand it. I'm just reminded of how strong that smell was I was actually gagging.
The tubs were heavy, the handles were feedble. Some of the tubs were damaged so I got a bit on me.
I stunk of it for the rest of the shift. It wasn't even a normal garlic smell it was just so powerful and nauseating.
I'm in a similar situation with "little drummer boy", irrespective of the group/ band covering it. My heart hurts when I hear the 'rumpa-pum-pum' and its been like this for decades. :(