What you can’t know about people
When you encounter a person on the street you can identify certain things about them right away. Their height. Their weight. How they walk. How they dress. Their general demeanor.
What you can’t know anything about are the experiences they have had in their life. Their childhood. Their career path. Their relationships. The events that have led them to this point. Why they are the way they are.
People like to hide this kind of stuff.
Passing judgement based upon what you see is easy. Trying to understand what you don’t is hard. Becoming aware that you are choosing one of these two options every time you encounter someone new is probably a good first step to take.