To be persistent in effort, unyielding
愚公移山
yúgōngyíshān

It literally means the Foolish Old Man who removed the mountains.

The Story:
There was once an old man in the ancient times, whose house stood facing two high mountains which made it very inconvenient for him to come and go. One day, he gathered his family and started to level the mountains. His neighbors, upon seeing him, laughed at him. "You are foolish. You are too old and weak to level a small hill, let alone two big mountains!" He replied, "I have sons, and my sons have sons. I will have endless progeny, but the mountains won't grow any higher." When Heaven heard the spirit of the Foolish Old Man, it was moved and sent two immortals to move the mountains away.