I enjoyed reading this blog post from Benny who is an expert on language acquisition and an inspiration to anyone who follows the polyglot trail.
I found myself nodding in agreement at several points. The languages that stick are the ones where you have emotional investment, that is why I have "forgotten" Norwegian, Italian and Welsh but so far, clung onto French and Spanish: they are the (only) languages that some of my friends speak. It’s obvious really, but for me seeing it written down made me realise it for the first time. So the message is clear, having got to conversational level I need to speak, read and think in English, French and Spanish every day, and all will be well.