Here's some advice from someone who's been there... but my horse was 16 (yes, I'm serious) not 6.
Finding a good dressage trainer that you and your horse both click with is very important. After every lesson, write down exactly what you learned. That way, in the future if you are having problems you can look back and say "Oh! I remember now!"Also, it is going to be hard! A year from now, if you get really frustrated, look back at how much you've done, and all the progress that you made.