painful lessons的用法和樣例：
例句
- Europe's plans for further unification may be up in the air, but people from Helsinki to Rome have been learning an often painful lesson in recent weeks about how entwined their economies have already become.
歐洲進一步統一的計劃可以尚未定案，可是從赫爾辛基到羅馬的人在最近幾星期得到一個時常令人痛苦的教訓：他們各國的經濟已經如何地牽扯在一起了。
