A smile costs nothing, but gives much, so always keep smiling!

微笑不需要花费什么，却能给予很多，所以永远保持微笑！

youdao

I do know how upset the shop staff can get, but I try to persuade them to keep smiling.

我知道店员会有多生气，但我努力说服他们保持微笑。

youdao

I didn't mean to keep smiling.

我不是刻意地保持微笑。

youdao

"The kids keep smiling every day, " says Tatsuya, with his little son perched on his lap.

BBC: Japan tsunami: Searching for the lost in Natori

He helped teach Raymond the finer points, including to keep smiling and to keep moving.

WSJ: 2 guys have a ball as Michael Jackson on Broadway

In the end, the most important thing you can do for your customers is to keep smiling.

FORBES: Connect