The Tommy Angelo article griffey refered to was called reciprocality and it applies a ton. Here it is
http://www.tommyangelo.com/articles/reciprocality.htm

It comes down to getting better requires people to find the spots that are costing them money. Your general winrate will come from not the 4 or 5 hands you play for stacks every session but the 20 or 30 hands that are in the 30-60BB range. The coolers and AA vs sets are hands that will always wash in the long run, are we really doing a ton better in these hands compared to villains to make our winrate that much more acceptable? Winning and losing long term in poker doesn't come from sets or JJ+(although learning to fold at the right times could help). Believe it or not, it will come from how you play a ton of hands below them.