Definitely speaking for me. I wouldn't be able to take time to calculate what is the proper way to make a sentence. Even when I speak my mother tongue, u sometimes make no sense. Though when I write, I can always look over what I wrote before send.
As far as I know the Chinese is the most difficult language to learn. There are too many characters(not words) to memorize. And it has 4 accents to be used... In my case, I couldn't even pronunciation some of the words.. just my case.
If I don't speak or read constantly, I tent to forget both languages. Now I am losing Korean words, because I don't use it as intensively as before, and also losing English cut I got lazy reading books and newspapers. OMG.
Whenever you learn from an actual person, i think it is impossible not to have an accent. The way I learned English was resembling my teachers' and friends' way of speaking. I have a southern accent, I think, not strong but do.