mkrnhr said:Practicing the language in situ offers a huge advantage, along with language affinities. I've known Spanish and Italian people who learned French within a few months while taking just a few lessons and mostly interacting with people.
Interesting point since I witnessed that too when I was studying English in university a few years ago. I remember an Italian young girl who told us she had not found French particularly difficult, except for silent letters. Of course, the fact that French is a Romance language and has a lot of vocabulary in common with those languages - and sometimes even conjugations - must have made her learning of the language a lot easier. The reverse happens with people born with a Germanic or Scandinavian language who find English quite easy since it has retained its Germanic roots, though having imported countless Romance words in the process (mainly from French after William the Conqueror had seized Normandy, since his aristocracy spoke mostly that language). A friend of mine is both French and German, though having lived in France for most of her professional life, and says that she's never had any trouble learning English.
To speak from my own personal experience, I do agree speaking with natives and having experience as an insider in the country gives a real boost to your language skills. It is also better since you catch the language as it is thriving at the moment, not as it has been frozen in textbooks, especially slang which evolves very very fast.