One and a half year ago I wanted to comment an article about a second language. Sometimes people are having hard time learning new things, and it's not just their fault, it could be literally an anomaly in the brain structure or it could be related to the level of complication of the language someone chose to learn.
To a personal background level, I believe I used to be a polyglot, a linguist if you will. I loved to learn new languages, I started English as a second language at the age of 9 (I think), all thanks to my wish to understand how to interact with the computer and read foreign literature. From there, I followed English until the GCE O'Level certificate. In the meantime, I began French for fun, having nothing to do during long summer days. The intensive 5-hour lessons proved to be a really attractive language and I continued learning for 3 consecutive years (during July/August). Then came preparation for the medical schools, which put a stop to all my other activities. Perhaps it was my teen-hormone years or my own free will that did not pursuit my love for new languages. Nevertheless, I've learned basic Latin and still continue to perfect my knowledge in Serbian language during my medical school years - I guess I still have a crave for languages deep down under the wish for wearing a white robe. :)
No hard feelings to anyone, but I've recently compared the Serbian language to the German. Not that I know much about the German language, but I've noticed that in German there is the possibility to mix multiple words into one. Really cool once you get to know the basics of the language, but sometimes it is really hard for new learners. Basically, the grammar and the word pronounciation can be a reason for a person to pull back and not wanting to express themselves in that language. For example, Serbians from what I know have a hard time using "th" or "th"(d) - i.e. in the words "theatre" or "the" respectively - in English, which I think is one of the reasons they prefer not to use English at all.
The fascinating thing as a child is that you can learn more stuff than an adult person, the so called "Tabula Rasa" thesis. My opinion is that gifted polyglots (people that speak a lot of languages) should nurture their languages by daily or weekly translating/reading text of headlines, otherwise the wealth of words and phrases of a language they might once perfectly knew will definitely decrease by time without giving it adequate practice. And it doesn't stop there, listening should adopt your hearing ability in order to rapidly process verbal requests or to better interact with other people. Remember, a dialogue needs "two to tango", so it might be better to find a partner for it. Exchanging opinions about your primary language for a secondary one through "The mixxer project" may prove really helpful. I haven't tried it yet, but some of the readers may have better solutions for this. I suppose that you'll have to make remarks about the difference in slang and normal language, so.. be very careful!
Learning languages can be compared to other learning possibilities, such as playing the piano or the guitar or even writing code in various programming languages. There's a time when you might mix up words or phrases, but the brain learns to eventually adopt while multi-processing such requests - almost similar to other mechanical functions, like driving, eating a burger, talking to the phone and switching gears at the same time (not that I recommend it).
To sum up, comparing time required, ability to learn and grace of use, as a child you'd have better results in learning a language, provided you often practice. And do practice, because in later years it will definitely prove worthy!