垂头丧气
Hang one's head.
Down in the mouth (dumps).
With one's tail between one's legs.
Look crestfallen.

eg：Robert hangs his head down because he lost in the competition.

中英俚语俗语来源：唐书：“失势者垂头丧气。”

同义词：没精打采 With the wind taken out of one's sails.
反义词：趾高气扬 Ride the high horse.