Watch Your Tone

I've started taking Vietnamese lessons. There's something like 3 different a's, 2 e's, 3 o's, 2 u's, along with 5 different tones (up, down, short, and the other 2 I can't even explain). All are equally difficult to say (and some are so similar I can't even hear the difference), and of course each word means something completely different if you say it wrong. My teacher is pleasantly suprised everytime I manage to say something correctly (and she also likes to laugh whenever something's said wrong). I'm thinking it's probably gonna be a while before I've reached fluency.