lighten up

1.He did his best to lighten things up.

他尽力使局势起来。

2.Come on, lighten up! It was only a joke.

喂，别紧张！这只不过是开玩笑。

3.She tried to lighten up her speech with a few jokes.

她讲几个笑话以使讲话轻松愉快些。