A healthy romantic relationship is based on interdependence. Codependence and interdependence are two very different dynamics.
Codependence is about giving away power over our self-esteem. Taking our self-definition and self-worth from outside or external sources is dysfunctional because it causes us to give power over how we feel about ourselves to people and forces which we cannot control.
If my self-esteem is based on people, places, and things; money, property, and prestige; looks, talent, intelligence; then I am set up to be a victim. People will not always do what I want them too; property can be destroyed by an earthquake or flood or fire; money can disappear in a stock market crash or bad investment; looks change as I get older. Everything changes. All outside or external conditions are temporary.
That is why it is so important to get in touch with our Spiritual connection. To start realizing that we have worth because we are children of God. That we are all part of the Eternal ONENESS that is the God Force/Goddess Energy/Great Spirit. We are Spiritual beings having a human experience - our worth as beings is not dependent upon any outer or external condition. We are Unconditionally Loved and we always have been.
The more we can start owning the Truth of who we really are and integrating it into our relationship with ourselves, the more we can enjoy this human experience that we are having. Then we can start learning how to be interdependent - how to give power away in conscious, healthy ways - because our self-worth is no longer dependent on outside sources.