If your heart is in your mouth, then you feel nervous or scared.其实“Heart in your mouth”的意思是感到紧张或害怕的。这是一个常用的英语习语，与中文“心悬在了嗓子眼”或者“吓得心脏都要跳出来了”表达的意思相近。我们也可以用“with one's heart in the mouth ”来表达某个人吓得不轻。
My heart was in my mouth when I went to the stage to make my first speech in front of all the people.
当我走上台,第一次在所有人面前演讲时，我紧张的心都快出来了。
Danny’s heart was in his mouth when he decided to try the roller coaster.
当丹妮决定做过山车时，他十分紧张。
心提到嘴巴里表示害怕，那么，"Down in the mouth"嘴巴向下表示什么呢?我们一起来学习一下。
If someone is down in the mouth, they look unhappy or depressed.我们知道，down 除了可以用来表达“下面”，还可以用为形容词，表示“沮丧的，不开心的”。坏心情都占据到了嘴巴里了，也就是说他极其的失落了。
-What's wrong with you, Daniel ? You look really down in the mouth for the whole day.
-Oh, I failed again in my math exam .
-你怎么了 Daniel? 你一整天都看起来很不开心。
-我数学考试又没有通过。
Rob has been down in the mouth ever since his parents divorced.自从Rob的父母离婚后，他一直闷闷不乐。
