How Can I Not Care Anymore?

I am pretty certain that I will never understand how
someone can so easily cut someone else out of his or her life with just a blink of an eye.  How in the world can a person go from being an important part of one’s life to nothing more than a distant memory, if anything? Maybe it is that I care too much for the people that come into my life and even those who leave my life with or without notice. Maybe I exert too much of my own energy on others; maybe I let my emotions get too involved when someone crosses my path. Regardless of how protective I am of my heart, it seems like it is never enough. No matter how hard I try, I cannot just forget about someone, especially someone who flooded so many of my thoughts and dreams and so much of my time and energy. I cannot write someone off without a second thought, yet I feel as though it is the norm nowadays. How? How is this so easy for so many others but not for me? Maybe I should try to change because it doesn’t seem like the others are willing to budge on this one. How can I begin to not care so much for others and only focus on my feelings and my well-being? What can I do differently so my heart doesn’t continue to feel like this for the period of the earthly life that God has set aside for me? It seems to work so well for everyone else, so how can I do this? I really need to stop getting hurt and consumed in the heartache that goes along with it. What’s the answer? How do I do this? And more importantly, will it ultimately make me feel better about myself and my life, or will it only bring me shame and more heartache? Help...