Only promise me that you will smile.

不过您得答应我，您一定要笑。

youdao

You will smile to everyone every day.

你每天会对着每个人微笑。

youdao

Then one fine day, you will smile to yourself.

然后在一个晴朗天，你将会对自己微笑。

youdao

But it will also be the smile, the smile that says you are welcome."

VOA: standard.2010.03.26

Within 20 degrees of separation from you initial smile to the three people, the entire world will be smiling.

只需要20度的分隔,从你用笑容感染三个人开始，全世界就会笑起来。

哈佛公开课 - 幸福课课程节选

Typically, someone who is in agreement with you will smile and nod as you speak. (Disagreement shows up in compressed or pursed lips, clenched jaw muscles, or a head turned slightly away, so eye contact becomes sidelong.) But smiles are often used as a polite response and to cover up other emotions.

FORBES: Body Language Savvy for Sales

You have one shot to make the best impression possible, because as you leave the room, someone else will brush past you and smile.

FORBES: What I Learned About Interviewing from Miss America

Some pictures will always make you smile.

NPR: The Iwo Jima Photograph