It's a strange feature of the way the mind works so that some images or comments stick and return to haunt us while others pass and are instantly forgotten. I recall once inadvertently seeing a sequence in the film Highlander - a sequence I'm not even going to detail here because I don't want to give it further mileage - which recurred like a nightmare for years. (I should add that I saw it without wanting to as the film was being watched on video in a classroom at the end of term when I happened to be looking for a book in the room. I simply looked up at the wrong moment).
And then of course other people think you're crazy for being affected. But maybe it's a warning against the chance stupid comment, the gratuitous insult, the sharing of information which is better kept unshared. For we never, ever know where it is going to resurface, and we have no idea of the lasting power of our thoughtless words to spoil and destroy.