Sun Tzu's story pretty much puts to rest the 'grass is greener' theory, doesn't it? I mean, he goes to parties, has friends, etc, and still isn't happy. So being cool, in itself, won't make you happy. Only your perspective on the world can make you happy.
Which is not to say that being 'cool' doesn't help. It's just not all there is to it. As to 'being yourself,' I think that's a phrase that has no meaning anymore. It's a cliche. You can't possibly be someone esle, so don't worry about it. I have found that people who won't do this or that because they are concerned about 'being themselves' aren't serious about self-improvement.
THere are some very simple rules to both being cool in high school, and making friends. Some of those rules sound pretty trite, but they're important nonetheless. For instance, fashion is important to being cool in HS. So, first step to being cool is finding out what's considered cool and learning about it. Going overboard is bad: Don't get entirely decked out in Tommy gear, or you'll stand out like a wannabe-sore thumb. But think about the small points of fashion and don't commit any major 'crimes' like wearing a pocket protector (or whatever is a faux pas these days). Start from there.
Use your better judgement and don't do anything really stupid, like drunk driving or whatever, just because you think it will make you friends. Fact is, people will respect you in the end for having a conscience.
Think critically about people. What do people look for in a friend? I think it's the ability to listen. Empathy. So, listen. Ask questions about things they want to talk about. If it's something you completely can't relate to, so much the better. THink about why the heck someone would be interested in that crap. THey have their reasons, and they're probably not as shallow as you might think at first. Go from there.
One can be cynical and say that what I've said above is 'faking it.' But it's not. THere's a big difference between posturing--trying too hard--and thinking critically about how the world works, and then applying that knowledge.
I personally couldn't give a rat's *** about fashion, but wearing relatively 'cool' clothes has the simple and desirable effect of allowing other people to concentrate on my personality. If others are silly enough to believe that my clothes have any connection at all with the kind of person I am, so much the better. It makes it easier for me to be myself, not harder. Besides, you can't fight fashion anyway, so use it to your advantage.
I'm not sure this is entirely on-topic here, but my mind hasn't been grounded by coffee yet
. Actually, there's an idea... E yous later!