I don't know if it's a very good lesson, but my discipline to tighten up my game from just opening up 4 2nl tables. Later that day i tried 6, then 8. By the next day i was 12 tabling and didn't really have time to think about anything else. I don't usually run that many tables anymore but I think doing it for a few sessions helped me get used to playing nitty and folding margional hands in margional situations.