Have you ever wondered...why not revive that new subject passion by picking up a second foreign language?
I don't think that double language acquisition is an impossible task at all. I learnt up to three languages at the same time between the ages of 14 and 21 and found it keeps things interesting over years. It's not unheard of to study whole groups of very similar languages together, such as the Romance languages (French, Italian, Romanian, Spanish..) or Arabic dialects. But double language learning should be handled with care. Here are some golden rules to help you put it all together successfully.
Commitment is one of the essential ingredients to any success in language learning. You have got to keep the study of language going for some time before you understand its structures and build up a nice comfortable level. Luca from polyglot dream calls this establishing a language core. Build up this core in foreign language 1, then avoid getting rusty through daily practice while you focus on foreign language 2.
For example, if you have studied German for some years and feel comfortable having a chat now, you may want to start putting energy into learning Italian. While you build up the core in Italian, make sure your German doesn't get neglected completely with podcasts, simple articles or songs.
This project is bound to demand a significant time commitment, and you will do well if you make yourself aware of this before you run out of steam. My tip is this: Think school curriculum! Draw yourself up a timetable. Schedule in every day's commitment load, whether it's a lesson with the tutor, an hour at college or even just 10 minutes of podcast listening.
This way, you can check back to what you assigned yourself on the days where you just feel stuck. The upshot of double language learning is double pride, so do put in that necessary discipline.
Immersion learning is the way to go for speed and progress in my eyes. You need to practice to acquire fluency, and through fluency your core becomes a lot more valuable. If you are learning more than one language at the same time, however, be careful not to overdo it. You don't want to gorge yourself on too many different languages. Instead, keep it simple. Not more than you can handle at the same time, unless you're in the business for inventing the latest Esperanto-style creole version of whatever you're targeting. Unfocused learning is just a waste of time.
You're setting yourself a great goal like "be fluent in two foreign languages by Christmas", but are you making sure your goals are realistic? Easy milestones are important. Time is on your side here, and please remember not to go into rushing the progress. I presume you're still going to work? Seeing your family? anguage learning can be achieved at incredible speeds, but people put their life on hold for this. Get the balance right before your ambition becomes a stress factor.
One final secret tip?
Revisit your own language! It's the one you know best and the one you can get to know in your own time, all without scrambling for a single word of vocabulary. With this and the first foreign language, you will develop your own way of understanding the structures that pop up again and again, and this logic is language learning gold. Getting the hang of what concept is to be put into words is half the battle won. Grammar rocks, remember?
For more detailed advice on how to build a really solid language learning system, try a Fluent Language Guide -- there's an audiobook and a set of ebooks for you on my book page.