Your best friend is the keeper of all things: your secrets, your life's highlights . . . your life's lowlights. They know the good and bad in you and will call you on it like no other because your connection is tight. Nothing comes between you two or threatens you two. Your attachment is, as psychologists say, secure. That's why there are just some things that only a best friend can say to you, and no one else — not even a love partner!