One thing I noticed when I studied with predominantly upper middle class people (business school) was that they all had what I like to call a competitive "winner" mentality.
Most went into new situations determined to win/succeed, and when I questioned some of my peers on this, I was told that most of them had received positive feedback (albeit being pushed) since they were kids, in most aspects of life. School, sports, social life, etc.
I guess that if you've had cheerleaders around you since you were 5, it must have affected your self-esteem in some positive way.
Now, what I wonder, is how regular people can develop such attitude, more or less on their own. Fake it 'til you make it? Incrementally become successful at things?