  Sleeping on Brushwood and Tasting Gall 卧薪尝胆

  
  In the Spring and Autumn Period, the State of Wu defeated the State of Yue, and took the king of Yue, Gou Jian, and his wife prisoner. For several years, Gou Jian laboured as a slave in Wu. When he was released and returned to Yue, Gou Jian was determined to take revenge for losing his state. So that he would never forget his humiliation, he slept on a pile of brushwood and tasted gall before every meal. After ten years of careful preparations, he attacked and finally conquered the State of Wu. 
  春秋时代，越国被吴国打败了。越王勾践和他的妻子都被带到吴国做苦工。后来勾践被放回越国，他立志要报亡国之仇。从此，他每天夜里睡在柴草上面，不用被褥。在他住的地方，悬挂着一个苦胆，吃饭前，都要尝一尝苦胆的味道，以提醒自己不忘过去的耻辱。经过十年的艰苦奋斗，越国终于战胜了吴国。

  This idiom is used to describe inspiring oneself and working hard to accomplish an ambition.
  "卧薪尝胆"这个成语用来形容刻苦自励，奋发图强。