Personality evolution?

An interesting exchange occurred tonight with my friend.  He mentioned that he would guess I might not get along naturally with some of his other friends, because we have quite different personalities.  I really wanted to know why, and he explained that they are more reserved, not so outgoing and interested in partying as me.

This was pretty amazing to hear, because for basically forever, I was much more like he described his friends than the way he described me.  Apparently, ever since I met him, I've portrayed a personality much unlike my old(?) characteristics of many years of my life.

I should probably take into account, though, that I nearly always meet him in a dance setting.  Such is cue for my general happy behavior, since, well, social dancing is kind of the best thing ever.