你走路当心点，别一直看着手机。

Nǐ zǒulù dāngxīn diǎn, bié yìzhí kànzhe shǒujī.

Watch where you’re going—don’t keep staring at your phone.

天气很冷，要当心着凉。

Tiānqì hěn lěng, yào dāngxīn zháoliáng.

It’s very cold—be careful not to catch a chill.

当心别摔倒了。

Dāngxīn bié shuāidǎo le.

Be careful not to slip and fall.