亡羊补牢 wángyángbǔláo

A man who raised sheep once noticed there was a hole in the walls of his sheepfold. But he neglected to repair it. A few days later, several sheep were missing. His friend advised him: "It is not too late to mend the sheepfold." "Wang Yang Bu Lao" or "Mending the sheepfold after the sheep have been stolen" advises us that even though we have suffered a loss, it is never too late to take steps to prevent further losses.

画龙点睛(hua long dian jing)

There was a painter in ancient China who was especially adept at painting dragons.  Many people, from emperors to Buddhist priests, hired him to decorate their residences, temples, and murals with his artwork.

One day, as the painter was finishing up a mural of four dragons, people walking by noticed that he left the eyes of the dragons unpainted.  “How come you are leaving the eyes blank?” the people asked.

The painter replied that if he drew the eyes of the dragons in, the dragons would fly away into the sky.  The people were incredulous and urged the painter to finish his mural, so the painter sighed and drew in the eyes of two of the four dragons.

As soon as he finished with the eyes of the second dragon, the clouds in the sky darkened and the winds began gusting.  Lightning streaked across the sky and at the clap of thunder that followed, the people saw the two dragons separate themselves from the mural, and fly up into the sky. 画龙点睛 later became a chengyu that indicated that extra touch, that special something, when used at a key moment in a process, (usually storytelling or essay-writing), that makes the work vivid and life-like for the audience or reader.