Qian Ju Hou Gong (Proud at first but humble afterwards)
During the Warring States Period, there lived a politician named Su Qin who tried to get a job as a governement official, but to no avail. His parents, his sister-in-law, and his wife were all ashamed of him, but it was his sister-in-law who treated him worst. She would ofter mock him, saying that he would never amount to anything.
Su Qin felt very hurt, but he did not lose hope. He studied hard every day, and finally discouvered what he called the "zong-heng" principle.
Su Qin traveled to many kingdoms explaining his ideas, and at first he was rejected everywhere he went. But his suggestion that the kingdoms of Yan, Chao, Qi, Chu, Wei and Han all unite to fight against Qin was heartily accepted in both Yan and Chao. What's more, the leaders of these two kingdoms asked him to go persuade the other four leaders to go along with the plan. Later, these six kingdoms were united, and Su Qin became their very well-known and highly respected prime minister. One time, he was passing through his home town, and his parents and sister-in-law all came out to welcome him. Su Qin laughed and sad to his sister-in-law, "You were always so arrogant; why is it that you've suddenly become huble?" His sister-in-law felt very ashamed.
Today, this idiom can be used to describe anyone wo acts haughtily towards another person, but then becomes respectful upon learning that that person is of high status.