Why does everyone leave? :(

In my life. Why. ): It's either some of them just walk out of my life soooo easily.
As if I meant nothing. Do you know how that feels?
Or some of them move or have to leave for a while.
It all started at the beginning of this year.
I lost a friend, because they were upset that I dated this boy.
They knew that he wasn't a good person to date. Especially with all the girls he liked and moved on previously before me. I was too selfish. And I wanted to be in a relationship with that person. So bad. I followed my heart and, I lost her. And I tried to make everything work out. But nothing ever did.
Now, look what happens. That boy has been lying to me, and hid many secrets.
That's not the way he is. It upsets me because..everything is different. He is different. My friends were right. They were yelling at me that he would hurt me and leave. And they wouldn't be there to make me feel better. :/ Ouch. That's harsh.
Why can't it be easier? Seriously. He has it waaaaaay easier. And he's being happy and everything. I don't think I deserve all of this...what did I do wrong? I don't understand.
I never had a chance. I guess everything, was fake. i didn't get a chance for something real. Because I was the girl who is left out in the cold.
Now. It's like. Should I be friends? Or not. Because..the friendship previously was awesome. Brother and sister-like. And I'm not the type of girl who can let go in a blink of an eye. It's too painful and I don't see how I can even let go. Part of me tells me I should, but the other is like no.
No one can help me with this part. And, it's the most difficult.
2 friends lost...
The others had to leave, or move. 3 of them.
And all 5 of them were all close to my heart.
But the one that hurts me the most is the one I mostly wrote about.
Is it okay to want something back?
....
No. I guess. :/