You seem to have a side in here that we never see in the other forums...and to be honest, I'm kinda liking it...
I do seem to act differently with different people. When I'm around my long time friends and those who know me as a crazy, fun-loving, laid back, not a care in the world then I act that way. But when I'm around people like Jenny and her friends, or some people who don't know me too well I seem more mature...in a weird way...unless the sugar has a hold on me...then I act the way I do around close friends etc.
And then there's the emotional side of me that is rarely if ever seen. Even I don't know enough of that side to give a description of it...it's a kinda me under all my exterior layers...if you get my drift.
I think recently I've been trying to be more polished than I actually am. So now there are people who look up to me as some sort of messiah figure, when I'm not all that great. So I'm going to turn it down a notch or two back to my 'regular' behavior.
I used to act similarly to you. As in, silly with friends, mature around others. Now I'm half and half, but the same with both types of people. More balanced, I guess.
I'd say it comes w/ maturity and age, being more of a constant "yourself". I was like that alot too depending on which friends I was with and I noticed that I did that so I slowly stopped, but I only noticed because I had been getting more in tune w/ myself as I got older.
You've actually got that pretty backwards, with maturity you learn what to hold back around certain people. For instance, you might be a pervert, but you don't act like one at grandma's house if you're mature.
I was talking about knowing yourself not how you act around people. For instance, as a 12 year old you might like to touch your little sisters ass, but the older you get and more mature you realize that, you are a pervert.