Speaking Arabic and Sango together, I notice that the set of words I know in the former are different from the set of words I know in the latter. Often, I'll start a sentence in one language and then want to plug the holes with words from the other. The main difference in the Arabic and Sango vocabularies I've accumulated concerns the body.
In Arabic, I studied for two semesters and have to wrack my brain to think of any body parts besides “heart,” which I only know because it appears in so many Arabic pop songs. In Sango, it sometimes seems like every sentence contains a word that also refers to a body part: “inside” is “in the stomach of,” “after” is “on the back of,” “center” is “heart,” and it goes on from there.
If, as I suspect, the copious body references in Sango and their lack in Arabic is a broader phenomenon than the limited knowledge within my head, I wonder whether that difference has an effect on how a native speaker of one or the other perceives the world. Perhaps it's just a marker of broader cultural traits. (Of course, in English the body part back and the directional marker back are the same, and I don't usually think of my spine when I tell someone “It's back there.” But a native speaker probably wouldn't be the one to notice these things.)
Mostly I just try not to let it all get too jumbled. Considering that in any given day I might write in English and Norwegian and speak in French, Sango, and Arabic I figure a bit of confusion is understandable. Getting to use all these languages is one of the things I really enjoy about my work.