Because my brain is as fried as a funnel cake.
I'm studying for the AGI - Advanced Ground Instructor - certificate, which qualifies me to teach flying on the ground. (Generally referred to by it's TLA (Three Letter Acronym), because the FAA (Federal Aviation Administration, though it used to be the Federal Aviation Agency, and prior to that, the CAB (the Civil Aeronautics Board) sure loves its TLA's.)
I may have gotten into this on a dare. Not confirming or denying, just mentioning it's a possibility, and wasn't exactly a long-range plan slowly coming to fruition or anything. The first few sections of the study suckered me in. Okay, Aerodynamics & Aircraft rattled my brain cage and shook a lot of dust off some schooling I haven't touched in a long time, and force me to hit the books and start studying up on the actual principles that had become rule-of-thumb or "Ah, I don't fly that, so I don't care."(Look: I know a lot about flying off gravel and sandbars, and very little about turboprops. What we don't use, we forget, and it's a very big aviation world out there, with lots of specialties, too. Aerobatics? Those are things I don't want my airplane to do, not things I am comfortable or familiar with.)
But that was cool; it was a heck of a challenge, but actually pretty interesting to relearn, and learn ways the field has changed since I started flying.
...and today I hit Weight & Balance & Aircraft Performance, and it hit back. Nobody warned me there'd be calculus! Or spaghetti charts! ...maybe it was because I failed to ask. *facepalm*
I'm almost to the end of the first round of question study and review. I can do this. I really can...
After I go rotate the cat, mow the lawn, do some laundry, and whatever else it takes to get the brain to stop making crackling and spluttering noises.