I think that fear of abandonment is self-perpetuating to some extent. I mean, some partners can handle insecurity in the other, but some people just don't want to deal with it. By stating our insecurities, it's almost like we have a 2-part goal -- to either preempt them, or to get them to prove something to us. Either way, it is very frustrating to be in a relationship with a person who doesn't trust or who often implies that we intend to abandon them. Nobody likes having words (or motives) put in their mouth.

When I was a teenager (younger than you, of course), I was very insecure and did a lot of the things you described. Only after sufficiently annoying some of the guys I dated did I make a conscientious effort (per the advice of a woman I worked with) to force myself to not say the words or ask the questions. It seems like an oversimplification, but the less I showed my insecurity, the less it took over our conversations, thereby deemphasizing it. Secure people are far more attractive (and less likely to be abandoned) that insecure people... therefore whatever we need to do to gain security in ourselves is a smart way to go. I don't know... I don't have better words to describe it and the word "habit" sounds kind of generic, but I think that a lot of it has to do with breaking a habit of being insecure. I know, I know, I know... it does sound oversimplified, but again, I'm not articulating what I mean very well right now. More coffee needed, maybe. But it's something to think about until more people chime in, ok?