I don't like learning things without understanding why they're true. Too many of my math classes have been like that - teaching facts and methods, and how to apply them, but not the underlying concepts. I always tried to reason out the underlying concepts for myself, which was sometimes quite arduous.
Imagine my delight when I arrived in a Calculus class with an emphasis on the underlying concepts! We did not simply learn the theorems; we proved them in class. What's more, learning calculus gave me a better perspective on the lower-level mathematics it relies on. There's no better way to gain an understanding for something than to be forced to put it to use. A lot of ideas that had been bouncing around in my head coalesced into a nice, concise unit.
Another thing I absolutely hate is knowing that something is calculable, but not knowing the mathematics to do it. AP Calculus was the most advanced class my school would offer, so this year I'm working on learning more independently. I get a lot out of math textbooks (preferably the old ones, which are more focused on getting the material across than trying to make it interesting to people who are genuinely not interested.)
Better yet, there's more interesting things about calculus than its use for calculation. Here's a beautiful example: Calculus draws no distinction between time and space. It is no easier to calculate the rate of travel of an object over time than to calculate the rate of time going by as it travels through space. Now, this isn't grounds to say that there is no distinction, but it is grounds to question any assumptions we have about the differences. For instance, what reason do we have for saying that the human typing this essay and the human attending Hastings Elementary School ten years ago are the "same person"?
It's easy to walk along this path, destroying assumption after assumption and arriving at apathetic nihilism. That is why we don't use mathematical logic for everything. In fact, there is a reason in my example: there's a particular type of strong causal relationship between those two humans. Such a relationship is easily referred to, in our language, as "being the same person"... I love building up ideas this way because they create practical definitions. For instance, this one easily handles the question, "If science could destroy a human in one place and recreate it in another, would it be the same person?"
Still, as a practical definition, rather than a purely logical one, it's possible to create borderline cases, and have a whole spectrum from "is the same person" to "is a different person". There seems to be no fundamental difference between them - which leads to the most interesting conclusion for me personally: that there's no fundamental difference between good planning and altruism (i.e. between helping future-"self" and future-"someone else"). If I have helped myself more than others, it is only because of purely practical limitations.