I tend to think of myself as naturally and nurtured submissive. I was raised in a very religious household by my grandparents, and as my mother's behavior essentially labeled her the troublemaker of the family, I was expected to be the counterpart - the good girl who was talented, excelled in school, etc. That's a lot of pressure on a child, and drove home a need to always behave, always excel, be a perfectionist, tightly rein in and control personal behavior, etc.
Add to this certain choices, such as joining the military, where discipline is a must, and working in EMS/FD where I am the highest trained in my ambulance and thus always in charge, and you have someone who is used to having to be in control. However, others have mentioned the personality change that I have when in that environment - it is a much different person that you see, because I have to change who I am to fit into the environment.
Times in my life when this self-control and in-charge attitude have been involuntarily taken away (such as illness at work) leaves me very lost and emotional. It's not pretty. But when given the opportunity to hand over control voluntarily, such as being a sub in a BDSM context, or a patient in a medfet context… that's different. It's very freeing. I'm allowed to let go because I know I can trust the play doc/Dom/Top I'm with at that time.
Rope bondage has been the most freeing experience I have ever had, and now not being in a context where I have the opportunity to be tied has its drawbacks. What once was a great outlet to let me be free has gone, and I've yet to really find anything to replace it.
Also, because I know what will happen if I don't add this disclaimer: no, I do not Top, and I have no interest in examining or Topping anyone.
Anyway, my $0.02.