Unless you've been hiding under a rock since 1983, the term "co-dependency" is probably familiar to you. However, like most psychological terms that make it to the pop-psychology world this one has been misused and abused to the point that most people don't really know what it means. You might think you only display symptoms of codependency if you are married to an addict or in an abusive relationship. However, one of the things I see often in my work as a marriage and family therapist that is extremely disruptive to the marital relationship is an inability to self-regulate or "be okay" without a partner carrying a part of that responsibility for us.
What in the world does that mean? That means, when I'm anxious because I feel like you don't love me or I feel insecure, my reaction is to blame my husband or require that he make me feel better or reassure me. Depending on what my childhood looked like, I might even start a fight to prove that you don't really love me or want me. Either of these eases my anxiety and puts the responsibility for my feelings on you instead of on me.
Pia Mellody in her book Facing CoDependency organizes codependency into five symptomatic categories. A person who is struggling in this area may have difficulty with the following (taken from her book).
1) Experiencing appropriate levels of self esteem
2) Setting functional boundaries
3) Owning and expressing their own reality
4) Taking care of their adult needs and wants
5) Experiencing and expressing their reality moderately
All of these issues typically stem from how we were raised. That doesn't mean you had "bad" parents, it just means you learned somethings that you probably should work on so that your current relationships can flourish and grow. Codependency is like a weed that chokes out intimacy and fullness of life.
Some things that a codependent might have difficulty acknowledging or acceptings.
1) I alone am responsible for my emotions and the behaviors they create.
2) No one can make me feel whole or happy. That comes from deep within and is the result of a really healthy self esteem and well developed self.
3) I am capable of holding the anxiety that is produced when I feel unsure or insecure.
4) The person hurting me does not need to experience my feeling or hurt the way I hurt.
Perhaps you have found yourself angry with a spouse because they have "made" you so angry as the result of a hurt or disappointment. If this is happening often in a relationship you might consider exploring the possibility that you resent your spouse for their inability to soothe your hurts/anxieties. This is codependent behavior. Note: abusive relationships are often codependent. I am not suggesting you are responsible for the abuse or should tolerate it. This discussion is solely about how codependecy could show up in otherwise healthy relationships.
The opposite of codependency is not isolation. The opposite is an awareness that relationships that are healthy are relationships where each partner is able to experience the five things Pia listed (above) and can mutually rely on one another for support, comfort and compansionship/friendship - not to fill holes that feel empty an hollow.
The more able you are to self soothe and handle your own insecurities and fears, the stronger and more resillient your relationships will be.
If any of this stings or hits a nerve, you might consider starting by reading Facing Codependency or Codependent No More. I think most people struggle with this a little bit. No need to label yourself "codependent" or worry that you're broken beyond repair. Simply acknowledge that perhaps there's undo pressure and unreasonable expectations being placed on others to solve problems that exist internally within you. The only person who can resolve those internal problems, hurts, wounds, holes is you. Consider also seeking out the help of a therapist to guide you in that process.