Relax, smile; loosen up in mind and body.

放松，微笑；身心俱放松。

I must take some exercise and loosen up my muscles.

我必须运动一下，放松放松肌肉。

The officials have been instructed to loosen up on the rules for admitting people into the country.

官员们接到指示，放宽入境规定。

Loosen up your muscles, please.

请放松您的肌肉。

Or should neat freaks loosen up?

还是洁癖鬼该放松一下？