不要信口胡说。

Don't talk at random.

那你说的那些什么“重新开始”之类的话呢？都是信口胡说？

What about all that "turning a new leaf" talk? Just nonsense?

笑具有传染性：这并非信口胡说：科学家说，笑容确实可以传染。

Smiles are contagious: It’s not just a saying: smiling really is contagious, scientists say.