Cool is something that cannot be worried about. Those who worry about how cool they dress are, nine times out of ten, not cool. They are posers. They are mannequins for their own fashion. The cool folks are the ones who simply do their thing and look the way that comes naturally to them. They don't worry about their "personal brand," but mayhaps they develop one anyway, simply because they are true to themselves.
Case in point: Bill Evans.
This is a photograph of pianist Bill Evans, one of the coolest guys ever. I listen to Bill Evans all the time when I write. His music is way at the top of my list. It moves me and makes me sad. He's the only white member of Miles Davis' famous sextet in the late 1950s and early 60s. His style was the single biggest influence on Davis' seminal album, "Kind of Blue." But look at the guy. He looks like an accountant who somehow wandered up on stage. Like he works hard to look as square as he does.
Here he is in the 1970s, much later in life. He had been seriously struggling with drugs for more than a decade by now and his career was more of a struggle, but look at him. You'd never say this guy didn't look cool. Ironically, the guy in the earlier pictures--the one who looked like a dork--that was Evans when he was at his best.
The moral of this story: Don't ever worry about cool. Cool is simply oppression in a black turtleneck.