"Finished up a block of _____ and wow my lifts increased big time!" Training max used.
Then a few weeks later, same poster:
"This block felt hard. I struggled during week ____ and missed a few reps. I've stalled" Training max not used this time.
I finished up a strength block last week and had some very nice increases on most of my #s (training max used). Then a few days later the little voice in my head started up....."You can do it without a training max, it's just a little bit more. More weight = more muscles = TB Cyborg mode"

I tend to be slightly OCD, and usually hold off on making even stupid small decisions until I feel like I've analyzed it from every angle....a mild form of paralysis by analysis. So I started searching up training max threads and going through logs. Almost every single time it seems the poster makes steady progress with a training max....then voila they drop it and run into stalls and incomplete reps, like clock-work.
Occam's razor guys? Perhaps Wendler, KB and others that recommend it are on to something?