to have a chip on one's shoulder

The phrase "to have a chip on one's shoulder" means to harbor a deep-seated and persistent sense of resentment or a feeling of being easily provoked or ready to take offense. It suggests that someone consistently perceives themselves as being treated unfairly or holds a grudge against others, leading them to be defensive or confrontational. This attitude often stems from past experiences or perceived disadvantages, causing the person to be constantly on guard or defensive in interactions with others.