Dumb and dumber

I feel like I'm losing my capacity to learn new things.

First, I held a meeting this morning (well, I was forced to, by upper mismanagement) which didn't cover much ground. It felt like my brain was unable to hold onto the topic; I was parsing sentences without understanding them.

Now, I'm trying to read some stuff on Mathematica's MathWorld site; for example, this discussion on fractal dimensions. I *know* that I was able to understand this, once upon a time. I could crank out problem sets regarding proofs of such concepts. Now I see a bunch of symbols and terms which form no concrete idea in my mind.

Perhaps I'm just losing my discipline -- that is, there's no incentive for me to study this, so I'm not putting the effort that used to come naturally into it. I'm worried, though, that it's deeper than that.