For extroverts like myself, opening up to people can certainly be much easier than for our introverted counterparts. There have been many times when I've wanted to stick my foot in my mouth, screaming internally because I know I've said too much. In these situations, it can feel very overwhelming when you realize that you've just divulged some personal information.
It can be very easy to start talking and not stop. In my case, talking to people is a doorway into new friendships -- it just gets difficult to close the door sometimes. I find myself rationalizing it all by thinking that the more open I am with someone, the closer I'll be to them, and that is a surefire way to friendship. Unfortunately, this isn't always the case. Some people just prefer not to interact on such a personal, intimate level, much to this extrovert's dismay.
Ultimately, all you need to do to avoid awkward situations is just watch your tongue. It's difficult at first, but I've found that the less you talk, the more you can listen. Listening will tip you off to just how deep someone is willing to delve into conversation. Take the social cues and don't try to overstep their boundaries. Instead, pick up what they put down and help them feel welcome by respecting their boundaries.