I don't know if you are using the word correctly either (or if there is a better word to describe it), but I find my self on the reactive side as well.

I know in my java lectures I'm kind of zoned out and don't really pick up much on the material being presented. But wait until lecture is over and the lab session is starting, and I tend to be all over it.

I think also, to answer your question about what you can do to be more active when learning new abstract concepts, I try to relate it to something familiar. I have a lot of trouble in the calculus class I'm currently in. But I feel like if I take a theorem or proof and relate it to a problem that needs to be solved in ruby or java, I'm able to think about it in a familiar way and can generally understand it better than before.