亡羊补牢 (wáng yáng bǔ láo)
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.