Believe it or not, it is true! The so called mannerisms that we create for ourselves may earn us a title of 'mature' if followed religiously, but that's where the story ends. Because more often than not in making an honest effort to be termed 'mature', you're not being yourself. Or put in a different way, you are not being honest with third parties in presenting your true complete self. So, basically you're being a hypocrite. And there lies the fun.
The thing is as we grow up, we may change in ways adults should change (what is supposed to be maturity) but all of us have our share of idiosyncrasies, and no one changes completely. If that were the case, then a given set of people would be likely to not like each other after say, a decade. In practicality though it doesn't happen. All of us have a bit of our 'childhood version' in us. And our earlier acquaintances relate with that to associate with us and use it as a benchmark to appreciate our adult version.
I've seen it happen so many times. With friends in Junior School. Friends of Senior School. Friends of College. Friends at work. And no doubt it will continue to be so. But, we all have set some norms in every society which is taken to be sacrosanct. Any divagation from it will raise eyebrows as that is what we have been brought up to believe. And it is because we are wary of this, we often try to be something we are not, and end up messing up images and relationships.
But will maintaining this two-sidedness always result in abject failure? The answer is NO. There are two types of people in this world - some who are good actors in life and some who are not so god at it. Those who are good actors might succeed in being labelled 'mature' without being termed a hypocrite. But those who fall into the latter category, surely at some point or the other end up with egg on their faces. As far as I have seen, most of us belong to the latter category and are living our lives day in and day out, constantly whipsawed by these dilemmas. What we choose to be is obviously only upto ourselves! ;)