It means the ability to say
This is who I am,
This is what I think,
This is what I feel,
This is what I want
without fear of judgment, punishment or rejection.
Essentially it refers to a person’s ability to feel and function like a self-supporting adult.
To the extent someone lacks this ability, he or she will tend to feel, inside, like a powerless child.
And to the extent either partner lacks this ability, relationships will tend to slip into what we call codependency.
Codependent relationships are characterized by anxiety, buried resentments, emotional disconnection, dishonest communication and compulsive controlling.
All common symptoms, unfortunately.
For which the only reliable cure is ego strength.