胆小如鼠
As timid as a mouse.

Cannot say 800 to a goose.
Afraid of one's own shadow.
Have one's heart in a nutshell.
To be chicken-hearted.
As timid as a rabbit.

eg：She is as timid as a mouse and does not know how to answer the question.

同义词：前怕狼，后怕虎 Too much taking heed is loss.
反义词：一身是胆 With plenty of guts.