All people can change the style of behavior depending on in what company they are. It quite naturally. However it is bad only if, changing the behavior you don't begin "to play a other role ". So, for example, going with girlfriends to cafe, you cheerfully laugh and without respite stir about everything on light. But, coming to work, you become more serious, reject thoughts "not on business" and talk only when it is necessary. Such behavior model is absolutely normal, any sane person understands that the situation otherwise provokes to concrete behavior.