成语力不从心：Ban Chao was a famous general in the Eastern Han dynasty. As the governor of Xi Yu (Western Regions, Central Asia), he made great contributions on expelling the Xiong Nu (the major enemy of Eastern Han) from central Asia, and opening and securing the trade routes to the west.

Due to the fact that Xi Yu was far away from Eastern Han, Ban Chao often had to fight with very few soldiers and supplies against strong enemies, but he skillfully played on their divisions among his opponents. By the policy of the stick and the carrot, he successfully brought the various people of Central Asia under Chinese rule during the second half of the 1st century.

His outstanding services helped him win the trust of Eastern Han court. Both Emperor and ministers thought of him irreplaceable. As a result, Ban Chao got enviable power and post, but on the other hand, he was stuck to his position, the governor of the most remote area of Han Empire. From a petty officer to the highest official, he had been working in Central Asia for thirty one years with no chance to visit his hometown, even when his mother died. bulaiya.com

As time passed by, Ban Chao became old and homesick. Though he had wrote many letters to the court, asking for retirement, all he got was nothing but meaningless comfort. Having no choice, he asked his sister Ban Zhao, a female historian and litterateur, to write to the Emperor directly.

In Ban Zhao's letter, there was a paragraph reading like this:

"Your Majesty, among all serving in the Xi Yu, my brother Ban Chao is the oldest. He is already over sixty, weak or sickly. His hair is white, hands are shaking, ears have been damaged, and eyes are not as piercing as before. Now he cannot walk without his stick. Once the enemies invade, I am afraid that Ban Chao might be unable to do as well as he wishes. At that time, imperial interests will be impacted, and Ban Chao's fame and achievements accumulated over years of faithful services will be ruined. How melancholy it will be!"

Moved by this letter, the Emperor finally allowed Ban Chao to retire. When he got back to Chang An, the capital of Eastern Han, after a long journey, Ban Chao was seventy one. Only a month later, he died.