have one’s heart in one’s mouth “心都快跳到嗓子眼了”，也就是“非常害怕”。

【例句】
I had my heart in my mouth when I heard he was sent to the hospital because of an accident.
当我听说他因为事故被送去医院时，我真的非常害怕。

Eric stood outside the door of his father's study and had his heart in his mouth, afraid to go in.
艾瑞克站在他爸爸的书房门外，心都提到嗓子眼儿了，不敢进去。