Self perception plays an extremely important role in how you appear to be in a physical sense. I have learnt this first hand after undergoing a massive transformation when I undertook the Australian BodyBlitz challenge. I'm no psychologist, but the way that you see yourself will greatly depend upon your self esteem.
I wrote this article, My Transformation - Exercise And Diet Just Isnt Enough which went through my personal experiences and how self perception plays an important role in determining your success or failure.
I think that a very hard thing to do is to learn to view yourself in the mirror objectively - this is why sometimes mirrors can be your best friend and photo's can be your worst enemy...or vice versa.