Marcos' answer was a great one!
I remember when I got deep into the English world and I started watching TV programs and I couldn't understand one single word. That was horrifying! C'mon, years of study for what?
The English language teaching in Brazil is very superficial, we're generally taught in a certain way that makes us learning several grammar structures without any applicability in the everyday English speech.
Watching TV and series is surely one of the best ways to get used to the real English, they're generally full of slangs, different structures, puns and most of the time use very trendy words and expressions. I'd like to give you another hint: Watch TV news. That's another way of getting used with everyday English, however, a little more formal. You're gonna get used with expressions that are more likely to come up in business vocabulary and could be really useful when it comes to using your English while working for a company that has English as one of its requirements. Having cable TV or even Netflix could be a powerful tool for that!
It's not an easy path at all cause it might take you a long time til you get good at that, but it's a sensational feeling when you start getting the results of your own effort!