You posted something — a photo, a video, a bit of yourself — and the comments were mostly fine. But one was mean. Just one. And that's the one your brain latched onto. You read it over and over, felt it sink in, and let it sour your entire day, even though dozens of people had been kind and only one had been cruel. You couldn't stop thinking about it. The one negative voice somehow drowned out all the positive ones, and you found yourself believing the meanest person was the one telling the truth.