So there's a frustrating thing with my native language: I speak it, but I don't *know* it.
With my other languages I'll often know the rule, or pattern, or origin, or principle behind a language construct. Because I had to learn it to learn the language.
But with my native language it's all "Dunno why. It just sounds right."
Which makes my native language the one I'm *least* qualified to teach, explain, or bend in creative ways.
@jannem
I disagree on that last one "bend in creative ways". A native speaker can play with the language in ways thay sound good in a way that someone formally trained will not have the ear for. I can often tell the difference between English written by different non-native speakers, such as a German or Japanese native, by the eay they bend English in different grammatical but oddly sounding ways.