Is there really a cure?

I am currently reading the book Codependent No More. Its a book given to me by my counselor years ago after I broke up with a boyfriend of 8 years. I don't think I had a problem before I met him but I know I definitely had a problem after. He was very controlling and possessive. He had a drug and alcohol problem that I tried desperately to fix, but couldn't. In the book, she states that codependency is: "An emotional, psychological, and behavioral condition that develops as a result of an individuals prolonged exposure to, and practice of, a set of oppressive rules-rules which prevent the open expression of feeling as well as the direct discussion of personal and interpersonal problems" Interesting....another definition -"Those self-defeating, learned behaviors or character defects that result in a diminished capacity to initiate or to participate in loving relationships." OK...I get it. I wonder how a normal, (well, somewhat normal) strong-willed, independent person becomes entangled in such a web?? How do we lose site of ourselves and become these people that the book defines? I wish I had the answer to that. I only know this, after leaving that relationship over 5 years ago, Ive had a hard time settling down with any ONE person for a long period of time. I did almost get married a couple years ago...I thought this guy was the one. I wasn't passionately in love with him, but he treated me like a queen. We were together for a year and a half, then, just when I let the barriers down and started to trust again, I found out he was a liar. A big one!! He didn't cheat or anything, he lied about money and stupid little things. It was habitual. I told him from the beginning, lying is the one trait I cant handle and he did it anyway. So, back to square one. Now, my trust issues have tripled and I trust no one. How do we get past the hurt and excess baggage so that we can learn to live healthy, productive lives in a wonderful relationship?? I have yet to figure this one out. The book promises a cure for this disorder...we shall see. Maybe I'm too old to be fixed? Has anyone read this book and will is really help??