Be careful lest you fall from that tree.

要当心，鎽以免从树上摔下来。

youdao

The Lord said to me: Say to them: Go not up, and fight not, for I am not with you: lest you fall before your enemies.

但上主对我说：「你告诉他们说：你们不要上去，不要作战，因为我不在你们中间，免得被敌人击败。」

youdao

As you look around you, you must feel not only the sense of duty done, but also you must feel anxiety lest you fall below the level of achievement.

放眼四顾，你不但觉得已经尽了应尽的责任，也感到忧虑，恐怕以后的成就未必能达到这样高的水平。

youdao

"There's an old social welfare quip: Beware the floor you set below which no one can fall lest it become the ceiling above which no one can rise, " Mr. Culhane said.

WSJ: Homeless Blame Game