1·This is a painful lesson.
这是一个惨痛的教训。
2·This has been a painful lesson to me.
对我来说，这是一个惨痛的教训。
3·This has been a painful lesson to me.
这对我是一次痛苦的教训。
4·This has been a painful lesson to me.
这是一种痛苦的疾病。
5·It's a painful lesson.
这是一个惨痛的教训。
6·We learned a painful lesson the hard way.
我们学到了痛苦的教训。
7·The painful lesson of Wenchuan earthquake should be remembered.
汶川地震的惨痛教训应予记起。
8·From my own experience, I draw a painful lesson HASTE MAKES WASTE.
从自己的经历中，我得出一个痛苦的教训：欲速则不达。
9·You are about to learn a painful lesson-you are both very selfish people.
你要汲取惨痛的教训——你们都是非常自私的人。
10·A painful lesson from Vietnam was the high cost of attacking heavily defended targets.
越战中的一个惨痛教训是，空军飞机攻击敌严密防卫的目标时伤亡惨重。