A: Tom complained with the management again about our department. He said we didn’t offer timely support to the sales guys. Couldn’t he be reasonable?

B: Why did you get so angry at the slightest criticism? You seem to have a chip on your shoulder.

Note: This idiom refers to a bad attitude that tends to get someone easily upset. Usually it’s about something that occurred in the past. The phrase reportedly originated with the 19th century U.S. practice of spoiling for a fight by carrying a chip of wood on one’s shoulder, daring others to knock it off.