那次事故给我们所有人上了严厉的一课。

That accident was a harsh ___lesson for all of us.

从这次失败中学到的教训将帮助我下次做得更好。

The ___lesson learned from this failure will help me do better next time.

他经常分享自己艰难时期的故事，这样我们就能从他的教训中学习。

He often shares stories of his difficult times so we can learn from his ___lesson.