The younger you are, the easier it is. But when you're older, it's tough! It happened to me: I learned fluent Spanish, then married an Italian. I got so confused, learning the new language, that now (not living with either on a daily basis) my language while visiting Spain/Mexico or Italy is quite laughable. But - they all understand me, so, hey! that's the point, eh?
It will come back to you when you immerse yourself in one language or the other, later. Meanwhile, take full opportunity of being able to learn a new language while you are there!