In the heat of the moment：If you say or do something in the heat of the moment, you say or do it without thinking because you are very angry or excited: （一时冲动、激动之下/盛怒之下）

E.G.1：What seems the obvious course of action in the heat of the moment isn’t necessarily the most effective one.

E.G.2：He lost his cool during the meeting and in the heat of the moment, shouted at his boss and called him names.