Innistrad (2011) - "Was the pinnacle of Limted set design."
The depth of the game and the ability to add on to the basic framework through the expansions is what keeps Jon engaged.
Not running enough lands in control decks and not playing 60 card decks.
Realizing that playing other decks outside your comfort zone can lead to growth and improvement as a player, not to mention better results.
Making first Pro Tour Top 8 at Chicago in 1997
Not being open to playing the best deck. Not playing Magic with the intention to improve. You need to be conscious of what you play and how you play so you can improve.