This is for English native speakers who are learning a foreign language(s).

I'd interested in learning what native English speakers think is one of the unique aspects of their native tongue?

Are there any expressions or words you can use in English but unable to do so in your target language(s)? Or vice versa? 

For example, would you be frustrated when you cannot express exactly although you know what to say, simply because the language you are studying lacks the corresponding expression?