I have a chronic language problem. I'm an over-accommodater, and it's sub-conscious.
Whenever I speak with someone I accommodate my language. This ranges from imitation of vocal range and accent, through to language structures. It's particularly acute when I speak with Mongolians in English. Firstly, whenever I am talking to, or even mentally thinking about talking to, Mongolians, my first instinct is to try to frame things in Mongolian. But sometimes I can't, I don't have either the vocabulary, or my brain is not quick enough to frame some more complex sentences, and then I revert to English. Also I have some Mongolian friends who just prefer to speak English. So when I speak English, I accommodate my English as well.
This drives my wife crazy.
Recently I was giving a talk to Mongolians, speaking English and using a translator. Because of this my level of accommodation was very high. And the result was that my English became very poor and ungrammatical. Especially, I drop almost all my articles. This is because Mongolian has neither definite or indefinite articles, so they're just cluttering up the airwaves!
Consciously, I can observe this phenomenon as it happens, but I find that it takes an extreme amount of control to counter-act it. Even when speaking with some very English-competent Mongolians, I will accommodate not to their level of English, but to my version Mongolian-English. Good thing I am not teaching English here.