I've come from Mathematics to General, and they are two completely different courses in my opinion. You may be doing very well in General, but do horrible when you move up to Mathematics. I suggest you look at some of the work, maybe you can get some off your friends that do Mathematics, and see whether you are up to it.
My Mathematics teacher always use to say that if you are in Mathematics, you should be a thinker. By that she meant that instead of just knowing a formula, you had to know why and be able to see it in other mathematic problems, you had to really think about the question. And you also should consider yourself a Mathematician. It does sound positive though, that you want to be motivated, because you will be in Mathematics.
Hope that helps!