For me, I can't think of a single biggest insight because right after one, another surfaces. Many of the posted insights here, either I have also experience or are new for me to consider. If I had to say one, it would be knowing there's another one that I have never considered. Being a social player and not playing a lot during the week, allows me the fortune of having tons of tips that slowing unfold to learn and improve my game.
My insight would be try to identify perfect technique and footwork, then measure yourself and strive for that. If you get that down and work on your strength and speed and practice loads the sky is the limit.
If you never get this down your potential will be low. A lot of people I see measure themselves purely on who they play and can beat at that particular time in their development rather than concentrating on playing correctly, refining their skills and developing far beyond. You can play bad and win games especially playing against familiar training partners. Basically don't get fooled, it stunts progress.
^ Huh? Don't we all already identify that LD and LCW have perfect technique and footwork? But strive as we towards that, nowhere do we get close... closer maybe, but not even close.
Haha yes I mean identify when you yourself are using correct or incorrect technique. Strange you should mention LCW here because I have exactly the same technique as him... when dealing with cramp after I play singles for any longer than 1 1/2 hours, just kind of bending down then getting stretchered off