In college, it was the “shrinking textbook” effect. Cramming for an exam, I knew I was in good shape when the amount of textbook material covered no longer seemed physically large and I started to remember where various facts and concepts were in the book. (Side note – turns out this was not a good marker of long-term recollection. But it was reliable for cramming purposes.)
In chess I wonder if it’s a good sign when boring stuff stops seeming boring. My drawn game last night was pretty insipid at one level – again I am trying to stuff my impulse to lash out in practically every position – but there were plenty of nuances that I need to dig into and fully understand, both in the closed/manuevering opening position and in the endgame position that was evolving when we buried the hatchet on move 30 or so.
When simplified positions become truly interesting, I’ll take that as a personal milepost that I’m getting to a different level of understanding.