I completely agree with Amira, I think it really helps if the languages are completely different and also different levels, if possible.
While I was at uni, I was studying German, Russian and Italian. German advanced, Russian and Italian beginner. I really enjoyed this juggling of languages, but of course, in the end, only German came out on top. I am now brushing up on my Italian, and did spend some months living in Russia last year.
For me it was about the experience of learning rather than reaching a specific language goal or level.