daigaku de benkyou shi<span></span>teta kedo wasurechatta

There are things about the adult brain that prevent most people from ever becoming fluent in another language. The cutoff date is sometime in your teens, if you ever want to speak another language fluently. So says Steven Pinker, anyways. Notice that babies can learn a language almost perfectly from scratch in a couple years. It'd take a decade to be good at Japanese for a native English speaker, in my opinion.