Ahhhh... I see. Not sure if the German course thing is analogous, but I think I understand what you experienced.
Although I was instilled with the importance of knowing the language of my heritage at an early age, I stopped speaking it around 10, so my vocubulary is rather limited and I certainly couldn't speak of anything in the abstract. As I got older and started traveling, I realized that when I spoke German in Germany, people would look at me in an odd way. It seemed that because I looked like an average German, I sounded vaguely retarded when attempting to communicate with strangers. So finally, after Christmas this year, I decided to buckle down, stop wasting my time with frivolous endeavors and learn the language properly. I even put a little German tagline under my avatar to remind me not to spend time here, rather study instead. It was hard as hell - certain things are easier to learn when very young... skiing, playing an instrument, learning a language. I studied, I passed, I have forgotten everything in two months.
Success with professional endeavors often has little to do with actually working hard.