How do I stop being so gullible and getting fooled?!?

I'm sick of my "friends", I've realized that I no longer have any friends that I can completely trust. I forgive them because I hate to be mad at people and I don't want negative energy... but this is getting out of control! I just want to be respected and for my friends to stop thinking that everything will be okay if they hurt me. I don't want to be cynical but how can I be better at not getting fooled by people?