To have extremely high aspirations, often to the point of being unrealistic or overly ambitious; to be excessively proud or conceited about one's abilities or potential.
她虽然只是一个普通员工，却心比天高，总觉得自己应该做更重要的事情。
Although she is just an ordinary employee, she has extremely high aspirations and always feels that she should be doing more important things.
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