Three years later, he led his army against the State of Yue and caught its king Gou Jian.
Fu took him to the State of Wu.
In order to avenge his father’s death, Fu let him to live in a shabby stone house by his fathers tomb and ordered him to raise horses for him.
Gou pretended to be loyal to Fu but he never forgot his humiliation.
Many years later, he was set free.
Gou secretly accumulated a military force after he went back to his own state.
In order to make himself tougher he slept on firewood and tasted a gall-bladder before having dinner and going to bed.
At the same time he administered his state carefully, developing agriculture and educating the people.
After a few years，his country became strong.
Then Gou seized a favorable opportunity to wipe off the State of Wu.
Later, people use it to describe one who endures self-imposed hardships to strengthen one’s resolve to realize one’s ambition.
5越王勾践为了使自己不忘记以前所受的耻辱，激励自己的斗志，以图将来报仇雪恨，回国后卧薪尝胆，最终东山再起，一举灭吴，恰恰印证了生于忧患死于安乐的观点。所以在我们遇到挫折后不气馁，不自暴自弃，受点委屈吃点苦头都没什么，只有心中有一股信念，只要活着，将来一定可以打出一片天地。
