How to keep studying foreign languages?

Hey everybody - I have taken cles in Spanish and Portuguese and I've been told never to take two language cles at the same time...so how can I maintain my level of proficiency in each? I'm currently enrolled in Portuguese and even though they're similar I still want to retain a strong understanding of Spanish. I also plan to learn a little French, Italian, or German later (at least reading comprehension) so I really want to keep practicing all 3 or 4 of those. Any tips or suggestions? I live in the US and it can be difficult to find communities that fluently and routinely speak those languages. Thanks!