I sometimes find myself using "beziehungsweise" in English because the English equivalents ("as the case may be", etc.) are often rather awkward.

I might start in a conversation or other situation thinking in English, but I shift pretty quickly to the learned language. Several years ago I was in Montreal and had begun to think in French. I saw a sign that read "men's suits" and tried to figure out which parts of the verbs mentir and suivre those were and why they would go together.

This happens to me with signs and the like as well. When I was intensely studying Irish, my first reaction to any new word with an even vaguely acceptable orthography according to Irish norms was to try to read it as if it were Irish. For instance, a co-worker drove me mad with a t-shirt for the D-beat band "Disfear" because I kept trying to read it as the future autonomous form of the non-existent Irish verb *dis.