You blame a persons behavior on their personality

Think back to the last time you got cut off in traffic. Did you say to yourself, Man, what an idiot, or did you think,Gee, she probably had a bad day. Chances are that you went with the former. In psychology circles this is known as the fundamental attribution error and it essentially states that while we blame the behavior of others on their internal attributes, we blame our own on the external. Sadly, even if you are aware of our predisposition towards making unfair judgements, it is notoriously hard to stop doing, so you will most likely continue making this fundamental error.