OK, so you have put in the time and can now speak a language at a confident level. But maybe the course that helped to get you there has ended, or your stay abroad is over and it's time to go home.
What do you do to make sure that you don't forget that language?
My own list of forgotten languages and understanding why
Something that is quite unique in my travels and lifestyle is the reason I have to learn a language of immediate use with natives in my travels, to enhance my cultural experience. This is not quite the same as many people, who choose their one language based on a long-term investment. A polyglot has many languages to deal with and this changes things significantly compared to someone with a one-language priority.
What this means is at the end of my 2-3 month projects to intensively learn a language that are more focused on an upcoming trip, I face a crossroad; should I maintain this language or not? Some people may take a “not” choice completely out of context and feel like the whole experience was worthless.
Every language I have learned has enhanced my travels in ways that I can't begin to express. Saying that any one of them was a waste of time is ignores the cultural experience that was my priority all along. I'm not passionate about languages, I'm passionate about using them.
Maintaining them as described below is so much work for such a large number that if that passion doesn't spark a lifelong interest in the language, then I simply will not prioritise it, since as a polyglot, I have quite a lot of languages to juggle! This is obviously not the same situation for someone who has learned one foreign language.
A consequence of this is that as much experience as I have in learning and speaking languages; seven of which I can now say I speak fluently, I have plenty of experience too in forgetting languages.
I have learned Hungarian, Czech, Catalan and Tagalog and could converse and socialise in all of them in various levels. But now I can't. Nowadays, I'd never even list them as languages that I can get by in to be honest. But I don't apologise for this or lose sleep over it. I knew it was going to happen.
So what did I do differently with my successfully maintained 7 languages compared to these?
The “secret” (no surprise) is simply consistently using the language so it is always fresh in your mind.
Of course you can come up with lazy excuses why this is not possible, but the truth is that you can always find ways to use those languages. Find natives to meet in person via social networks, use certain sites to find people to talk to by Skype, be friendlier with tourists, join clubs and actively monitor your social circle and environment for opportunities to use the language. All of these are ways you can speak your language immediately.
To maintain other aspects (reading, writing, listening etc.), the best way to maintain these is by doing them. Listen to podcasts in the target language, read blogs or online news or an entire book in that language, keep in touch with your foreign friends by chatting to them on Facebook or writing them emails; but do this every day.
The language will deteriorate in your mind if you don't keep it active. Having learned it “once” does not mean you now own it forever; use it or lose it!
Speed of learning
As far as I can tell, there is only one major disadvantage to my rapid learning strategy: the quicker you learn it, the quicker you'll forget it. This may sound bad, but it's way better than the alternative of learning so slowly you have nothing to show for it, ever.
If you dive in intensively into your language learning project, and reach high conversational level or fluency after a few months, then you have to be sure that you are consistently maintaining it until it is definitely a permanent part of you. I found with the languages listed above that within just a few months, I could forget the vast majority of my ability to communicate in these languages; I forgot it as quickly as I learned it.
So if you learned your language over years (actually using it, not simply being present in a classroom for something that could only laughably be called “years”), then you will be much less likely to forget it as quick. Spanish is the language I've put the most time into for example, and I am confident that I could cut myself off from the language entirely for a year (for example) and get back into it no problem. I've spoken and lived through Spanish so much that it's burned into me.
But the point is that I wouldn't cut myself off from Spanish. Why would I do that? If you genuinely want to speak a language for life, it will always be there for you to use. Even with almost a two-digit number of languages competing for time with me, I will always give the important ones the time they deserve (what makes a language important depends on you, not some economic etc. criteria or what someone else says).
With this in mind, even though I'm certainly aware of the danger of forgetting a language quicker due to learning it quicker, I still think this hardly counts as a “disadvantage”. You'll only forget it if you aren't using it. This is true whether you learned it quickly or slowly, only the speed of deterioration is different. After I had learned the other languages in my list quickly and intensively, I have kept up the good work of consistently using them and I will never forget them because of that.
Passion and the why
The main reason I will never forget my eight languages and certain future ones I take on, while I will forget others, is because I am passionate about the former beyond a fixed point in time when they served me a purpose of cultural immersion. That one thing, the why that sparked a flame inside me during my experience in the country, means that I will never let it go.
If you don't want to ever forget a given language, don't ever let it go. Make it an important part of your life; reading books and keeping in touch with friends is never a chore, but something that would leave a huge hole in your life if taken away.