... it turns out that my huge besetting problem, all these years, and which has prevented me from playing in any professional capacity, is an inability to stay focused while playing- it's still a problem. While sightreading, learning sections, or even with polished, memorized pieces, it' s a problem, still a problem. I can get through about two pages of music without pausing, stopping, "glitching," messing up- seemingly due to losing focus.
... I should just be humble and stick with my smaller pieces that are never beyond 2, or at the very upper end of my capacity, 4 pages.