What happened to best friends?

You said that we would be best friends forever
I believed you
You said that no matter what would happen, that you'd always be at my side
I believed you
You told me that when ever i needed someone to burden on you'll be right there with a shoulder for me to cry on
I believed you
But yet when i need you the most which is right now you leave me for this guy and i have no one
i loved you as if you were my own sister and you left me
i was always there for you when you needed me the most and you turned around and just left me here with nothing but a pillow that will be soaked and smelly by the end of today.
You lied not once but more then you know.
And now i have nothing....
You said we'd be best friends till the end...
What happened?