Wolfgang Pauli and Neils Bohr formulated the expression of a rule that governs the chemistry and physics of atoms called the Aufbau Principle. Stated simply, the principle is that elections fill an atom's various orbitals in order of lowest energy to highest energy. They will not add in any other way- i.e. they must "build up". In fact, this is what Aufbau means- "building up" in German.
In a sense, it can be a metaphor for the learning experience. You cannot learn physical chemistry without physics, you cannot learn physics without calculus, you cannot learn calculus without algebra, and so forth. You can of course, but it is more difficult, and ultimately you will struggle for proficiency rather than mastery. I can teach someone to do simple derivatives by teaching them the various rules regarding powers. An eight-year-old could learn that 2x^2 should be rewritten 4x and how to solve simple problems by rote.
I'm happy with what I'm learning now, and after a little bit of hectic discombobulation while I was in catch-up mode due to illness, I'm back to full sails and smooth waters. Still, that's a little boring, and sometimes I find myself very curious about various phenomena that I won't get around to until later classes. I get antsy, in other words. It's okay when it manifests itself in extreme nerd behavior involving studying for next semester, but it's a little sad when I'm in the library at nine o'clock in the evening looking up stuff on a ten year old textbook for something that may be very out of my league. My friends think I'm insane, and I have to agree a little.
It's a sort of stir-crazy: Ultimately, It's a consequence of stasis. I've been in school too long. A late change of major means I'm aching to exit the undergraduate world- without much regard to where I'm headed afterwords. Meanwhile, I'm stuck to going one semester at a time, and things are moving abhorrently slow. It's not a rut, it's not a case of me being down in the dumps. I'm actually quite excited and engaged by most of the material I'm learning. It's just that I sometimes get this inescapable anxiety, similar to the feeling like you're in an elevator that just taking a just little too much time to get where it's going.
Basically, I have to be patient- it's not like I have a choice. Really, the only thing I can do about it is gripe a little. I'm hoping to join up with a lab as an undergrad assistant soon (hopefully sometime after this summer) and that will help immensely. Meanwhile, I'll be attending class after class, building...