When one is a teacher, there are several nuggets of experience to chew and internalise and one such nugget is the act of being kind and free with the students. When it comes to interacting with students inside and outside the classroom, I make it a point not to be very strict or reprimand them for every single act of theirs. Even while teaching, my examples are drawn from everyday aspects of life that the students can relate and sympathise. And the smile - I almost always have a smile pasted on my face which tends to make the student comfortable while in the class and also during our different interactions.
The smile is always mistaken as a sign of extreme tolerance on my part and also the green signal to flout certain disciplinary boundaries. I understand that I cannot expect my students to observe every single thing that is normally expected of them like sitting quiet in class, fidgeting with mobiles and trying to do their homework when I am teaching. But my friendly behaviour and pleasant demeanour makes them think that they can get away with whatever they are doing.