I don't know how to use discretion, and it's affecting my friendships.

I don't know why but I've always had a hard time lying, and no matter what information just comes straight out of me. Sometimes it's hard because I try to spare people's feelings, and try to keep my friends together. But I accidentally cause my friends to fight because I can't keep secrets from anyone. I am an open book, and always upfront with people. I don't share information maliciously, but I don't know how to stop myself.