With mathematics, like with any subject matter, for me, what is important for a gifted person, is depth as well as breadth. The depth part is the so satisfying. You almost get a chance to feel like, "What was that person working on when they discovered a theorem?"
This week we looked at the formula for the volume of a cone and pyramid as always being one-third of that of a cylinder and rectangular prism, respectively, given the same dimensions. But, the materials do not tell the student who discovered that and how. So, if we have time we can look it up on our own. Was there a sculpture and they chiseled it and took the measurements? We don't know.
So, for any class, I would look at the materials. Estimate how much time the child will spend with that book that semester. Look at the entire schedule, figure out sleep requirements. (My child debates me about sleep. So, it is on our list to read the latest sleep studies.)
Then, figure out what your goal is. For me personally, I think of that time with a book as my chance to absorb that book and possibly never read it again. I would love to have time to reread everything that I want, but days go incredibly fast.
I am always thinking about a model where you have these great materials from a young age and you study them for years instead of semesters.
The other point is how good is your memory. This generation seems to be under the impression, because of their technology, that they can look everything up when they want to. But, in the course of a day, if the info. you need is in a digital book and not in your head, will you have time to look everything up? I don't think so. So, I always throw in the possibility of solar flares that take away our technology of today and put us back to doing things with our brains as the spell-checker and calculator and grammar-expert, etc.
Really try to get in touch with your feelings. Some people say that if it feels too daunting, they have to do it. Some people say that if you are waking up concerned, then it's a no-go.
I wouldn't get so hung up on grades; it's more about enjoying the learning and keeping your level of balance.