Pain and Torture...self-induced

Why is it that the people we care about the most are normally the ones that hurt us the most as well? How can it be that someone you consider to be your closest friend doesn't consider you their closest, even worse they don't even try to keep your friendship? It's been so long since I have written and I have been through so much that I don't want to remember it. Suffice to say that my summer was nothing but waves of sadness and hatred pointed at one person. Then they turn around and tell me, basically, that they aren't going to try and reconcile our friendship and won't be hanging out with me because "her grades suffered so much". If her grades had truly been suffering she could have said something last semester and to put it on me hurts. My grades suffered too...in fact I'm on probation because of my grades and yet I'm not going to push away my friends and I'm not going to turn into a complete witch. Apparently all of my pain is self-induced because i expect too much and put too much pressure on this one person and they cannot support me that way; my expectations were and are pretty simple. I expect them to be themself around me and to give me some time to talk when i need to talk. I don't ask for much...and yet it seems as though they cannot give me any time to talk about the problems going on in my life because their problems are so much bigger and more important. It hurts even more because I told them everything and explained how they were hurting me and it still didn't sink in...HOW MUCH MORE DO I HAVE TO SAY?! Actually nothing...I have stopped talking to her but it is so hard because i still consider her to be my best friend, and I would like nothing better than to sit down with her. But I cannot do that because I cannot put this pain aside any longer; instead I am ignoring her until she realizes how good she had it when she was my best friend. I'm not trying to be vain and say that I'm the best but I'm probably the only person who would give her anything and everything she asked for without asking for anything but a few words in return. It is so hard not talking to my best friend...every time I see her I want to hug her and say I'm sorry but it would be a lie because I'm only sorry that once again I let someone into my life and heart that just turned around and stabbed me.