这封信好似一剂苦口良药。用英语怎么说？

这封信好似一剂苦口良药。

The letter had a very salutary effect.

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

letter

n. 信，证书，许可证，字母，文字，字面意义；vt. 用字母标明，写字母于，加标题；vi. 写印刷体字母；

例句
Naylor acknowledged, in a letter to the judge, that he was a drug addict...
内勒在给法官的信中承认自己吸毒。

had

v. 有（ have的过去式和过去分词 ），（亲属关系中）接受，拿，买到；

例句
He claimed that his parents had abandoned him...
他声称父母遗弃了他。

very

adj. 很，非常，恰好是，正是，十足的，特有的；adv. 很，非常，充分，完全；

例句
Most people have very little difficulty in seeing why a Van Gogh is a work of genius.
多数人不难理解为什么凡·高的作品是天才之作。

salutary

adj. 有益的，效果好的；

例句
It was a salutary experience to be in the minority...
敌众我寡时倒是可以磨炼人。

effect

n. 影响，效果，印象，所有物；vt. 使发生，引起，产生（效果）；

例句
The police said Mr Hadfield's decision would have no adverse effect on the progress of the investigation...
警方称哈德菲尔德先生的决定将不会对调查的进展造成不利影响。