Keep something for a rainy day.
未雨綢繆。

Great minds think alike.
英雄所見略同。

Every flow must have its ebb.
人有悲歡離合，月有陰晴圓缺。

Empty vessels make the most sound.
滿瓶不響半瓶響叮噹。

Give a dog a bad name and hang him.
欲加之罪，何患無辭。

New brooms sweep clean.
新官上任三把火。

A good conscience is a safe pillow.
良心清白，安枕無憂。

All that glitters is not gold.
虛有其表。

If you wish good advice, consult an old man.
老馬識途。

Don’t teach your grandmother to suck eggs.
別班門弄斧。