Trusting friends - getting over betrayal?

I have lost a bunch of close friends in recent months. One of the things that hurts so much so finding out that they have lied to me about things. How do you trust friends? You think you know someone and then they turn on you. One of my closest friends had told me things I thought were true, only to find out that information was left out or the story twisted to make her look good. I just don't know who to trust anymore. Sometimes friendship are not worth the pain.