【成语来源】 

It is never too late to mend.
亡羊补牢

Once upon a time, there was a shepherd who kept several sheep.
从前有个人,养了几只羊。

One morning, the shepherd discovered that one of his sheep was missing.It turned out that, during the night, a wolf had stolen his sheep through a hole in the sheep pen.
一天早上,他发现少了一只羊。原来羊圈破了个窟窿,夜间狼从窟窿里钻进来把羊叼走了。

His neighbor suggested to him: "You should fix the pen and cover the hole right away."
邻居劝告他说:“赶快把羊圈修一修,堵上那个窟窿吧。”

But the shepherd said: "The sheep is already lost, so I don't need to repair it." And so he rejected the neighbor's suggestion.
他说:“羊已经丢了,还修羊圈干什么呢?”他没接受邻居的劝告。

The next morning, he discovered that another sheep was missing.Once again, the wolf stole the sheep through the hole in the fence.
第二天早上,他去放羊,发现又少了一只羊。原来狼又从窟窿里钻进来把羊叼走了。

The shepherd regretted not taking the neighbor's advice.So he plugged the hole to secure the sheep pen.
他很后悔没有接受邻居的劝告,他赶快堵上那个窟窿,把羊圈修得结结实实的。

From then on, no more sheep was stolen by the wolf.
从此,他的羊再没有被狼叼走了。

【文化链接】

“亡羊补牢”这个故事中的主人公虽然因为不听他人意见,而使自己蒙受了损失,但是后来经过自己的补救,使同样的情况没有再发生,所以现在我们常用这个成语表达“出现了问题,只要及时补救,都还来得及”。
英语中如果想表达同样的意思,我们可以说“It is never too late to mend.”,也就是“补救永远不嫌太晚”。