Fashion is what you adopt when you don't know who you are.
Fashion is a way of not having to decide who you are. Style is deciding who you are and being able to perpetuate it.
Fashion is not style. Nay, we can say more: Fashion is instead of style. Style is an idiom springing spontaneously from the personality but deliberately maintained. If you have no personality, you may be able to save your face and, possibly, your entire anatomy by following the current fashion, but all we shall know about you, when we see you coming down the street, is that you had enough money to buy a glossy magazine and were sufficiently cunning to work out the cut of the garments shown therein.