That apparent contradiction is really what makes cool so hard. It's not just about being amped up at 10 or being a bump on the log at 0. It's about being a 10 at where you're going while you make it look like you're at 0. You kick ass, but you make it look like it's easy and you're not trying.
One of the best entrepreneurs I've ever worked with had that quality. The guy was focused like a laser on where he was going, but I never saw him get upset or look like he wasn't in control of himself and the given situation. He exuded "cool" and he attracted people like a magnet.
"Cool" is undefinable and you also need to consider one thing. Look a the number of cool people you've known who are unsuccessful because they view being cool as a priority rather than other things in their lives. A lot of people I went to school with 20 years ago are in basically the same jobs they got when they left school. They earned money at that time which seemed amazing to people with no income, got to do more fun stuff because they had the money etc.
Fast forward 20 years and they're in the same place. Just the "uncool" kids have overtaken them by a long way.
It's about finding the RIGHT people to hang out with not just ones who seem cool. If you're 20, your idea of cool is different to when you're 35.
MY advice would be to hang around with people that challenge you because that is really what people need.
The image I carry is of a special forces soldier in movies/tv: "the situation is not what we prepared for. crap. okay, let's move forward with our skillset."
Trying to emulate this in bad situations seems to always work out to my benefit, even though I'm not being shot at. Accept your situation, and start problem solving from it, not from what you expected. This is an amazingly important skill and gives what results in the air of relaxed and unflappable. That is what I think the author is labeling as cool.
It's not about "cool" in terms of having the right sneakers or knowing the best band on the cusp of fame that only a couple hundred people listen to ("I listened to them before they were big, man ..."). That's hipster cool, teenager cool, and it's ephemeral and ultimately has almost nothing real at stake.
Instead, it's "cool" in terms of "cool under fire" - having self-assurance and confidence to know whatever happens, no matter what that is, I'll handle it. Or I'll handle the consequences of not handling it.
That latter kind of cool is what you need to lead men into combat, win an Olympic medal, or start a meaningful and profitable company. It's coolness dedicated to a mission, a purpose.
Can't one be cool without being concerned about appearance?
I think coolness is about how one responds to situations, esp those unexpected.
Think about how people talk to gate agents when their flight gets cancelled. Those that are reasonable and rational are cool (as in cool headed). Those that yell are not. They also tend to get more of what they desire while not making enemies.
The definition of cool should not be stuck in a 15 year old's perspective of jocks vs. nerds.
One of the best entrepreneurs I've ever worked with had that quality. The guy was focused like a laser on where he was going, but I never saw him get upset or look like he wasn't in control of himself and the given situation. He exuded "cool" and he attracted people like a magnet.