"Yes, indeed. But what if it's too late? What if breaking up makes you realize that the person was really the one?"
Living in fear of change, and living with shoulda, coulda, wouldas is limiting to our development. If that person was really the one, then there is always the chance that life will bring you together again. If you find that the person was really the one, after soooo much deliberation and consideration before breaking up, I would be surprised frankly. But, if you find yourself in that position, and have no chance to get back in a relationship with that person, you could spend the rest of your days living in regret and mentally reliving the past OR you could learn from the situation and be better able to handle similar situations in the future. Being held hostage by the fear that one day you will wake up and realize that the person was "the one" is limiting behavior based on fear.
Resistance to change and fear-based responses are natural reactions, but often not the best reactions for our well-being/development. Thank heavens that great minds of history have surpassed the resistance to change thing in themselves and in the greater society so that we, as humans, keep developing in social structure, our understanding of the world, communication abilities, science, philosophy, and all the around growth of our species/minds. Granted, not all of these changes are good, but critical thinking and the transfer of power toward individuals are definately some high points IMO. At the same time, we still have a long way to go:)