This is where many people get tripped up. “But what do you mean it has nothing to do with me? They think I’m stupid! How can I let that go without being hurt by it?”
There are many responses to this. An energetic response might say that you have been holding that perception of yourself for such a long time (not your rational adult mind, but your wounded inner child mind) that you are sending out that signal and it is then being reflected back to you. The other person has nothing to do with it other than being a mirror for your life.
The psychological perspective might say that the other person comes to this (erroneous) conclusion based on all the experiences they have had in their life, and based on how they think about, perceive, interpret and/or frame those experiences. I would add that for most of us, the way we perceive the world around us was taught to us by our parents in childhood. We learn their belief systems, their values, and we continue to take in the world around us based on those beliefs, even as adults. This is why it is so important for us to examine how we think and what we feel and believe. Without this examination, we are merely living our lives through the lens of our parents. And so, when we are judged by another, it is a perception that comes from an amalgam of their interpretations often based on unexamined thoughts and beliefs. And the other’s judgment of me really has nothing to do with the truth of who I am, but has everything to do with the perception the other person has of me based on their life experiences.
I am not saying to never look at what another person offers you as reflection about yourself. Take it in, think about it, but decide for yourself if you have anything to learn from this. If needed speak with a trusted friend to help you with a level of objectivity around it. But through all of this processing, do your best not to take the information personally. If there is something to learn from the information, this is an opportunity to grow and there is no need for you to be in pain. If the information is a judgment that offers no truth about you, let it go.