"Maybe I'm gonna have a petite moment"

Recently, I was watching re-runs of The Real Housewives of New York City, when Kelly said something that made me laugh, and then got me thinking.  She had a stylist come in to her closet to pull everything that was old or unnecessary (which turned out to be a LOT) to donate to charity.  While her stylist was going through this 6-foot tall, former model's closet, she pulled out a cardigan, looked at the tag, and said "Kelly, this is a petite medium.  You are not petite.  You are never going to be petite.  Get rid of everything that's petite."  To this, Kelly, without hesitation replied, "Don't tell me I'm not petite!  Maybe I'm gonna have a petite moment!"  

I was struck by this, since so often I have moments when I'll pick up a piece of clothing in a store that I think is great, and might buy.  But then, I have to stop myself, and say, "Wait a minute.  This would not fit your body-type in a million years.  You were just not built to fit into this.  Someone was, but not you."  Why is it that we so often fool ourselves into thinking that we have a body that we simply do not?  And is there a way to target train areas of our bodies to change our so-called "natural body-type"?  Or is there necessarily a limit, of which the upper and lower boundaries are weight?  This is something I'd like to explore more in the future, as I hone my diet and exercise plan to fit the kind of figure of health that I wish to exude.