Our best versions
Can love grow on soil that is not fertile?
One of the more frequent models I have seen in my life is co-dependency where two both partners look for the other one to fill their needs. This cannot properly work since the only person who can repair your own issues is yourself. It is why the tandem of two people who are secure and content in their own skin is so rare and why I have met few couples who meet this criterion.
One can become convinced that co-dependency works because the fear of being alone is such an overriding concern for so many that it serves as prime directive. In this scenario, the individual will tolerate dysfunction simply to not feel isolated. Most of us need tending to childhood issues which impede us from loving ourselves fully such that without this remedy we cannot adequately love someone else. It is why so many relationships are only as healthy as the weakest link in the chain which is the partner in most need.
Once we learn to truly love ourselves then we are ready to enter a union to become the best versions of ourselves.