Ever since losing that match, he's had a chip on his shoulder attitude towards every opponent.

chip on his shoulder 是一个英语习语。chip 原指"木屑、碎片"，这里比喻"心理上的疙瘩"；shoulder 是"肩膀"的意思。 这个习语源自19世纪美国的一种习俗：有人会把木屑放在肩膀上挑衅别人来打掉它，表示随时准备打架。现在用来形容"长期心怀不满、容易发怒"的心理状态。 整个短语形容一个人因为过去的失败或委屈而持续表现出敌意或易怒的态度。