Yes, when I said 'be yourself' I was certainly referring to relationships. But that doesn't make it a useless cliche for getting sex either. The nub of it is that when you meet a girl, 9 times out of 10 she will get an idea in her head about you VERY quickly. And she'll basically try and let you know if she thinks you look like an interesting sort of guy. What comes next is largely up to the guy. Being yourself is so important because 1) she'll usually detect your sincerity and this will make her feel comfortable, 2) unless you have self-image problems, being yourself should by definition mean that you'll be comfortable as well, not to mention confident, and 3) if you two hit it off properly, your relationship or even friendship can truly blossom because things went so good from the start. First impressions, good or otherwise, tend to make a big impact on girls and can take a lot of time to alter, so I repeat...be your friggin self!
Of course, this is just in my experience so it would be wrong of me to try and apply this to all females across time and space. But I believe there's some truth in what I've just said. Try it!
Oh and a quick note to all those guys who are simply interested in unlocking some magic formula to a girl's pants - maybe there is such a formula, maybe there isn't. but as far as i'm concerned, even having passionate sex with the hottest supermodels this planet has to offer wouldn't compare to the sheer joy of sex between two people who are deeply in love with one another. Now THAT'S something that shouldn't be a secret!