Great question, and I think your comment about telling a story about who we are holds part of the answer.
Who we are is constantly changing. We get older; we have children, or we don't have children, we get promoted, we get fired, we work from home, we gain weight, we lose weight, we undergo loss and experience family crisis. Our story evolves
I think we use different tools or devices to tell our story at different times. Maybe its jeans for the years we telecommute, power suits for when we're promoted to Director of somethingorother, and athletic wear for the year we spend traveling the world in our Winnebago.
But I do think there is some almost intangible way of doing things (our "style" of doing things) that stays with us throughout. That's what leads us to choose the pieces we choose. My jeans look won't be the same as yours; my suit look won't be the same as yours -- but I bet there are similarities in how I choose my jeans and how I choose my suits or in the way I put those outfits together -- colours, necklines, hemlines, fits, pattern mixes (or no mixes), drape, texture... the list could get long.
I'm way heavier than I used to be, and I can't wear the fashion shoes that used to be part of my toolkit, so I have to find other ways to express my style with the current set of tools available to me.
Hits and misses are part of the journey -- I think each time we have to adapt we can expect we might get it not quite right sometimes. The sweater we thought was the new way to express ourselves told totally the wrong story (!).
Many, many years ago I worked in retail ladies wear, and I was always interested to see how the same outfit could look so different on different people. It came from how they carried themselves, how they saw themselves in the outfit, how they accessorized it. A dress could look dowdy on one 5'6" client and FAB on the next, even if it fit both of them. I think it was just that it aligned with one client's style but not with that of the other.
Style isn't so much about what's trendy or classic, it's about the choices we make and the unique way each of us carries it and pulls it together -- whether it's jeans or ballgowns. I suppose the more we know ourselves, the more true we can be to expressing our personal style and not just regurgitating trends.
Wow, I was very long winded there and not sure I added value, but I definitely had fun thinking about your question!