Sometimes I see people on the DuoLingo forums say that they ultimately want to become fluent in the language they're studying. That strikes me as a lofty ambition.
For someone living in the country of the language they're learning, fluency as a goal makes sense, and in my opinion is probably achievable. Most language learners and teachers agree that the best way to become fluent is to immerse oneself in the language, and the best way to do that is by living in a country where it's spoken.
For someone not living in a country where their language is spoken, fluency must surely be much harder to achieve. Independent study, including reading and watching television programmes in the target language, can increase proficiency (I can't imagine there's such a think as bad exposure to a language) but ultimately the way to fluency is to hear native speakers. Language, after all, is defined by its use as much as its rules. Language learning with no exposure to its actual use can, however, lead to the sort of hilarity found in the classic English As She Is Spoke.
I think goals need to be achievable and realistic in order to avoid discouragement. It's better to set a low bar, reach it, and then move on to the next target with a sense of acheivement than to reach too high and become discouraged at an apparent lack of success.
My goal with Welsh is definitely not to become fluent. Not at the moment, anyway. I don't think I'd stand a chance without being surrounded by Welsh speakers and using it every day. My aim is simply to be good enough to understand all the Welsh signs when I'm visiting Wales, to be able to conduct a simple transaction in a shop (actually I'm not that far off, if all I want is a coffee!) and to be able to read novels aimed at learners.