Chip on your shoulder

The phrase "chip on your shoulder" refers to someone who harbors a grudge or carries a perceived grievance, often due to feeling slighted, disrespected, or wronged in some way. It implies a defensive attitude and a readiness to engage in conflict or prove oneself in order to overcome the perceived injustice or inequality. This metaphorical "chip" represents the weight of the person's anger, resentment, or unresolved issues, which they metaphorically carry on their shoulder.