"Does your head start hurting when you computate math, or do any long drawn out science, english, or history"

The neurons are firing, the dendrites are waving their appendiges, and growing new ones, there is a whole lot going on up there. The hurt though has to be weighed against the good going on. It has been discovered that contrary to previous "knowledge", the brain continues to grow new connections, new memories all through life. The more you have, the better off you are. So, look forward to the hurt of new learning. It really is preparing you for a good life. Your brain is "you" more than anything else in your body.

Learning isn't the only thing to persue though. Trying new things, going new places, exploring your world are the other things that help make your brain excel. People who live near water have been more advanced as communities because the fish supply an oil that the brain can use to insulate the hard working nerves.

We shall never cease our exploration

And, at the end of our exploration

We will return to where we started

And understand it for the first time.

T.S. Elliot

But a lot of the reason for that is that I have read science and math books enough to be familiar with what they're saying and where they're going. I don't know everything, but I know enough to be able to see whether I can understand this or need to know more information/definitions of terms. This comes with time and exposure to the material. While you are learning the material, this can happen more than one would like. Thus, I say <qwertytheqwer> (great screen name> that you should neither panic nor back away from this challenge. Your brain is doing a lot of work right now that you aren't aware of and it will eventually become clear. Keep memorizing and keep learning.