Let sleeping dogs lie.

例句：

1. 1. I think it's best to let sleeping dogs lie and not disturb them.
   我认为最好让睡着的狗继续睡，不要打扰他们。
2. 2. The old man was so tired that he couldn't keep his eyes open, so I let sleeping dogs lie for him.
   老人太累了，睁不开眼睛，所以我让他继续睡。
3. 3. The dog was so exhausted from running all night that it didn't even want to get up, so I let sleeping dogslie for it.
   那只狗因为一整夜奔跑而疲惫不堪，甚至不想起床，所以我让它继续睡。