不能直译,参考如下:
I'm taught a lesson that people should never let down their friends.
百度教育团队【海纳百川团】为您解答,若帮了您,记得采纳哦-,0
never ever disappoint your friends.never ever let your friends down.
I have seen the truth in the saying that you should never let your friends disappointed(down)
I've come to realize that one should never let his friends down. 口语化的翻译方式,说出来要地道、顺口。希望对你有帮助。