Be careful you don't knock your head on this low beam.

小心，别把头撞在这矮梁上。

《牛津词典》

Be careful you don't bump your head.

留神别撞了头。

《牛津词典》

Be careful you don't trip up on the step.

你小心别在台阶上绊倒了。

《牛津词典》

But you must be careful. It is easy to get lost in the waves of moving sand especially during sandstorms.

VOA: special.2010.01.04

I love chemistry now. Be very careful what you say. Have any of you made that statement about hating a subject?

我现在很喜欢化学,所以你们说话的时候,可要小心咯？

麻省理工公开课 - 化学原理课程节选

So it's a way of reminding you, I've got to be careful about the types of things that I put in.

因此我这是在提醒你，一定要对输入的东西的类型,多加注意。

麻省理工公开课 - 计算机科学及编程导论课程节选

Ms. ARETHA FRANKLIN (Singer): (Singing) I ain't gonna be able be the loser my way, be careful you don't lose yours, you better think.

NPR: Oprah on a Plane �� for Obama

Less a case of be careful what you wish for, than be very, very careful what you wish for just before an election.

BBC: The third rail of Welsh politics

But the vast majority come from other, less rigorously overlooked, stores and so the general advice is to be careful who you buy from and then be careful what access (for example to SMS privileges) you give code that you do indeed download.

FORBES: Mac and Android Users Beware: The Malware is Coming For You!