cold feet 胆怯，打退堂鼓，信心或勇气的丧失

　　He planned to talk to Mary, but then he got cold feet.

　　他本打算去跟Mary说话，但后来临阵退缩了。

　　This is not the time to get cold feet. Let's do it!

　　现在不是打退堂鼓的时候，行动吧！

　　疯狂练习吧！