I served as an LDS (Mormon) missionary for two years in southern Argentina... basically I was just dumped in a foreign country and expected to pick up the language. It didn't take long for me to be able to say what I wanted, but to understand what people were saying to me took about 4 months for things to start clicking in my brain. It's crazy how it works but you just slowly are able to understand more and more everyday. I remember my first day there I got in a taxi and this guy was just rambling to me about who knows what... I felt so screwed. But then one day I was sitting in some tiny mud house having a full conversation with this family eating cow stomach thinking, "I totally understand everything these people are saying.. and I have no idea how."
I had some grammar books and some verb lists and a pocket dictionary. Whenever I heard a word that I didn't understand I would write it down, then go home and look it up. I would add this word to my vocab list (which grew to be like 10,000 words long) and would study it and try to use it the next day. After 730 days, you can learn a lot of words.
1. You learn faster when you have NO CHOICE but to learn or just be clueless to everything going on around you. This is the best motivation. If you just kinda want to learn, you will probably learn colors and "I like pizza" then be done with it.
2. You will most likely never be able to fully understand what people are saying to you unless you are fully submerged in the language. Honestly, I don't think just listening to radio or watching TV is enough. And things like Rosetta stone, will do little to nothing for you when it comes to comprehension.