I think the science bit posted by GuDe explains a lot about my relationship with my ex. We dated for 9 years and overcame so many obstacles together - moving halfway accross the country in my crappy car, helping each other build foundations for our careers, living together for 5 years, and building our own family. These things don't just go away over time. Add to that the fact we were together through our late adolescent years and almost all of our 20s, and I think there is a very strong chance we will reconcile.
However, I can't put my life on hold. I've taken more ownership of my life than I ever had before - finances, career, hobbies, interests, new people, and other women. It's all coming together rather organically and I'm finally seeing the truly wonderful opportunity that this time in my life is.