What's lost is lost. 失者不可复得。

What's done cannot be undone. 生米煮成熟饭了。

What is learned in the cradle is carried to the grave. 儿时所学，终生难忘。

Whatever you do, do with all your might. 不管做什么，都要一心一意。

Wet behind the ears. 乳臭未干。

We should never remember the benefits we have offered nor forget the favor received. 自己的好事别去提，别人的恩惠要铭记。

We shall never have friends if we expect to find them without fault. 欲求完美无缺的朋友必然成为孤家寡人。

We never know the worth of water till the well is dry. 井干方知水可贵。

Well begun is half done. 好的开始，是成功的一半。

We know not what is good until we have lost it. 好东西，失去了才明白。