"Happiness is just that simple" 这个短语来自一种对生活简单态度的诠释，表明快乐可以从简单的事情中获得。

一些相关的英文例句及其中文翻译：

Life is too short to worry about the pttle things, happiness is just that simple.
生活太短，不该为小事担忧，快乐就是这么简单。

Don't overthink things, happiness is just that simple.
不要过分思考，快乐就是这么简单。

Sometimes, all it takes is a smile to turn your day around, happiness is just that simple.
有时，只需微笑就能改变你的一天，快乐就是这么简单。