Ken - almost all of what you write matches what I've been thinking and feeling while riding. These techniques have what has worked for me in the past. Seeing it again in writing will help me focus again.

I know the feeling of pushing butt into saddle and pushing pedals through entire stroke, especially the up.
It's the transition I suddenly can't deal with anymore. I too like to pull up on pedals, a full even stroke, but that also increases speed, suddenly* I get this desire to slow cadence and its like I can't transition from pulling to resisting pedals evenly, then I get that out of control feeling, I panic and want to lock up. That is where the lower ration practice that transition is good advice.

*Suddenly - this I think is the mental problem, I think oh my its not gonna happen again and the faster speed it happens at the more concerned I get. Again the practice can regain that confidence.

I'm glad I posted (my too wordy ) thoughts on this. I thought others may not get it, but it seems it came across. I was hesitant given all the joking going on around here.

It just bugs me, why now after all these thousands of miles and many previous (very) enjoyable fast spins down the same hills? Nothing is different as far as I know.

I've never been a person prone to anxiety or panic, maybe its my turn for a bit.

Al