Caught Off Guard

My Italian mid-term is Friday, and it's hard to believe the class is already half-over. But I'm not worried about the exam. When I'm in class, I think I do pretty good speaking and interpreting Italian. I never have to ask the professor to repeat himself, and he rarely has to ask the same of me. But when I'm talking to an Italian outside of class, I get all flustered and things don't come out right. The other day, I was talking to a contractor about a natural gas line. As he left, I tried to say, "Grazie mille," or "A thousand thanks," but it came out "Grazie mio," or "Thank you, me." I'm sure he knew what I meant, and most Italians appreciate it as long as you put forth an effort. I just don't want try to say, "Excuse me, but where is the train station?" and have it come out, "Excuse me, but was your sister's face rearranged with a pickaxe?"