It's important to be careful.

小心是很重要的。

I always told him to be careful.

我总是告诉他要小心。

Remember to be careful all the time.

记得时刻小心。

Walkers have to be careful because the weather can change suddenly.

徒步者必须小心，因为天气可能突然变化。

Be careful not to be injured.

小心点，不要受伤。

I told him to be careful.

我告诉他要小心。

My mother tells me to be careful.

我妈妈告诉我要小心。

I remind you to be careful once again.

我再一次提醒你要小心。

We need to be careful with this project.

我们需要对这个项目上心。

I told you again and again to be careful.

我一再告诉你要小心。