The first is that if you kind of know another language, the fastest way to become more fluent is to get drunk or angry. Doing that drops your normal barriers to looking foolish and you are willing to try. And it probably works. (Of course too much drink or too much anger causes even experienced speakers to become incoherent in time...)

The second is an interesting theory about why children are so good at learning languages, but adults find it much harder. The reason is that parents and children both desperately want to communicate. If mothers could meet their children half-way, they would. But that would result in a private shared culture and language, and the children would never learn to talk properly. So while both sides desperately want to make communication work, it is important that the kids are the ones who have to come all of the way and learn to talk like grown-ups do. And so the parents inability to learn is necessary for language and culture to get transmitted to the next generation.

I don't know if the theory is right or not, but it sure sounds plausible to every parent I have mentioned it to...