Let sleeping dogs lie. 別惹麻煩
Leave something alone if it might cause trouble.
Jill: Should I ask the boss if he's upset about my performance?
Jane: If he hasn't said anything about it, just let sleeping dogs lie.
吉爾:我應該問問老闆是不是對我的表現不滿意嗎?
簡:如果他什麼都沒說，就別惹麻煩了。
You can’t teach an old dog new tricks. 老狗學不會新把戲；很難讓人改變
My grandmother doesn’t want a computer. She says you can’t teach an old dog new tricks.
我奶奶不想要電腦。她說老狗學不會新把戲（老了很難改變）。
a dog in the manger /ˈmeɪndʒər/
佔著馬槽不給馬吃草的狗；佔著茅坑不拉屎的人
someone who prevents you from enjoying something that they themselves have no need for
The little kid, like a dog in the manger, refused to get away from the study where her elder sister needed to focus on her homework.
那小孩有點佔著茅坑不拉屎，呆在書房裡不走，她姐姐可是要在裡邊專心做作業的！