Psychologists talk about people who are co-dependent because they don’t have a sense of self. What psychologists mean when they say a person has no sense of self is very different from what the Buddha meant by no-self or selflessness. People with psychological problems actually have a very strong sense of self in the Buddhist sense, although they may not in the psychological sense of the word. Psychologically, they don’t see themselves as efficacious individuals in the world, but they still have a very strong sense of “I”: “I am worthless.” When somebody criticizes them, they don’t like it. They get into co-dependent relationships to protect or to please this “I.” When they fall into self-pity, their sense of an inherently existent “I” is very strong. Thus they still have self-grasping even though they lack a psychologically healthy sense of self.
Buddhism recognizes two kinds of sense of self. There’s one sense of self that is healthy and necessary to be efficacious on the path. The object of this sense of self is the conventionally existent “I.” The other sense of self grasps at an inherently existent self that never has and never will exist. Within Buddhism, when we talk about realizing emptiness, we’re negating the false self, this self that appears inherently existent to us.
— Thubten Chodron – Cultivating a Compassionate Heart: The Yoga Method of Chenrezig