I'm a GM playing in someone else's game.
I've pretty much done nothing but GM since 1995 when I bowed out of a large Star Wars D6 RPG group and started up a smaller group playing Warhammer FRP. Since then I've done nothing but GM. On average I was running 3 games a week just about every week of the year. That's at least 306 games. Then I was running two games a year for the next five years. That's another 520 games. After that it petered out slightly, around about one game every two weeks.
So now I'm into gaming again but as a player... but I can't get out of GM mode! It's frustrating - all I want to do is sit down and roll some dice and enjoy the game but I keep catching myself, thinking 'I wouldn't have done it that way' or 'I would have introduced such-and-such at this point' or 'I would have played that NPC like this...'
Do you see what I mean? The game is great fun and I have no complaints about the way it's being handled by the more than competent GM we have at the moment, but I guess that more than ten years of conditioning is going to be hard to break away from. All I need to remember is that I need to keep my big fat mouth shut or I'm going to get kicked in the balls.