Why do people take things too personally sometimes?

Self-image. I've spent my whole life learning the hard way to be tactful and diplomatic. Each of us has built ourselves up as a mix of skills, achievements & faith-commitments that we consider laudable & right or wrong, we resist change & criticism. To try to get a new behavior from someone, praise, teach skills, give new true facts, appreciate who they are -- works better, gets less anger. Dale carnegie.