A lot of codependency looks very honorable to the outside world. They see someone taking care of a sick spouse and see it as an act of love... but when does this giving love turn into receiving abuse? There are so many extremes with it that a person quickly loss their own identity.
I have gotten so involved in making the life of another complete, that I have lost mine. The image below is a chart with the extremes of codependency while the middle shows the traits of a healthy relationship.