Dressing beautifully isn't about the clothes you wear or the face and body that you have. It's about being secure in your identity, about being confident and accepting of all the things you are (and are not). This self-awareness combined with self-confidence is then reflected in your attitude towards fashion.

Example, a woman wearing a white t-shirt and a pair of jeans. She can leave the house thinking, "Oh gosh I look so plain and boring", "My shirt makes me look fat", or worse "I'm wearing this so I don't get any attention because I'm not worthy of any attention". She'd be hunched down and timid when dealing with people, and others won't really see her outfit beyond how she sees it herself. 

But then she can also see it differently.