Why don't I want a "relationship"?

In a nutshell, I'm tired of being hurt.

I have opened my life, and my heart, too many times just to have a knife stabbed into my back. I've given, sacrificed even, listened to, been caring, supportive and understanding time after time only to have the one with whom I have become smitten turn around and cut me off completely. And on more than one occasion attempt to physically harm me!
I have heard every excuse there is. There is always a 'reason' that we can't be together right now...
I've even been told...and I quote..."I know in my heart that one day we will be together, it could be next week or next month or next year, but we will be together." Right...and I am Bill frikkin Gates!!
I seem to always fall for those who are emotionally, or just mentally, unavailable...either that or they are just mental..!!! And for some crazy reason I always believe when I'm told I am loved.
Sure, things can seem to be working out just fine for a while. I've even married some of them. But every time it has come to an end. Sometimes it's painful for them, some times not. But it always hurts me. Sure, I have ended a relationship or two, and even cut them off at the first sign of her emotions being more than I want at the time. But I was always honest about it and said that I just didn't want that kind of relationship...several of them are still good friends with me to this day. Others, well, I have no idea...
My point is:
I have done it for the last time. I will not allow myself to enter another "relationship" like I've had in the past. I will continue to be a friend who listens and lends a shoulder when needed, and I will be supportive of decisions to be made. However, I will no longer allow myself to be put in a position where the potential for heartbreak will happen to me again.
I'm done. Fini. færdig. τελικό. מוגמר. acabado. kumaliza.
Finished with the traditional "relationship". I'm not willing to allow the kind of utter sadness and humiliation I have already endured to happen again.
This may sound harsh, cold, insensitive, or just mean...sorry...it's how I feel. The ones I have met lately, and some from the past with whom I still communicate, know most of this already. Some, as expected, still do not understand why...so, there it is. The "Why"....

I'm sure I could edit this to add more... but without going into greater detail than already stated, just know this: my reason stands.

Feel free to email questions or even suggestions, just don't try to convince me to feel any differently or try to change my mind. I'm to the point in my life where the only person I HAVE to make happy is ME...and I like it this way...