I've found that the greatest difference between young people learning a foreign language and adults, especially older ones, is that the older you get, the less willing you are to say something that's wrong. So you spend a lot of time NOT saying anything instead of just communicating and letting the correct grammar and vocabulary come as it may.
This is what I think my biggest problem is. Once I get over making mistakes I actually quite capable of speaking the language. I was silent the first few days because I was so scared that people wouldn't understand me or I'd mess up. Once I got over that fear I was actually able to get around and say what I needed to say.
I really think I just need to practice and be forced to speak Spanish more often.