卧薪尝胆 wòxīnchángdǎn to undergo hardships to achieve an ambition
(idiom) to sleep on brushwood and taste gall; to endure hardships and persevere with resolve in order to achieve a goal or seek revenge. Historically refers to King [[勾践|勾踐|gou1 jian4]] of the State of Yue after his defeat by the State of Wu.