We should learn a lesson from our mistakes so as to be a better person in the future.

我们要从错误中吸取教训，以便在将来成为更好的人。

I hope they learn a lesson from this.

我希望他们能从中得到教训。

We must learn a lesson from this thing.

从这件事上我们要总结经验。

We should learn a lesson from our mistakes.

我们要从错误中吸取教训。

They should learn a lesson from this incident.

他们应从这事中吸取教训。