"Style is knowing who you are, what you want to say, and
not giving a damn." ~Orson Wells
I recently read a very succinct description of the difference between fashion and style: fashion is the relationship to the external, while style is the relationship to the internal.
The fashion oriented person is more concerned with whether or not the clothing they wear is similar to what they see out in the world. With fashion the emphasis is on the clothing; it distances the individual from themselves; it's perhaps a way of specifically not expressing self. The style oriented person, however, is primarily concerned with what's inside themselves- their sense of self and expressing their personal aesthetic. The style oriented person is more concerned with pleasing themselves than meeting an external standard.
It may be for some that self expression takes too much courage. For some however, not expressing oneself is too confining. (That would be me.) Others just have no desire to express themselves, and enjoy the constant change that fashion provides. I think in the long run style is more personally rewarding. I think the human animal needs to express themselves, to some degree, in some way, even if not via their clothing. Either way, it's important to respect what colors and design lines flatter you- that helps you put your best foot forward in the world, no matter what your position on style or fashion.
Another consideration is cost, obviously. If you're determined to follow fashion you're committing to buying a substantial portion of your wardrobe anew every season. If you can afford that, more power to you. The rest of us need to have more restraint in our choices. Even if I had that kind of money I think I'd rather invest it than blow it on clothing I was going to get rid of every season. But then again, should the fashion-oriented person donate those clothes to various thrift shops, style oriented (and/or less financially endowed) folks like me will happily pick up their cast offs the next season …
Like I said, I think personal expression, i.e. 'style' is more rewarding than following fashion, but I'm always one to champion what makes you happy- so if it makes you happy to follow fashion, then that's exactly what you should do.
Either way, it's good to be clear on the difference.