co-dependency = trying to control others
I'm not certain that this isn't too simplistic an answer. My thought on this is more co-dependency = anticipating people's needs (even if they don't
know they need it) so I don't get killed because I did the wrong thing.
I think perfectionism is a big thing that intertwines with this as well. It has to really. Being perfect is life saving as well.
And each of these things rely on external cues for validation. This is the crux of the matter as to why one can't tend to their own needs.
My needs = get me killed
Your needs = if you are happy while I make sure they are satisfied in you - keep me alive
As a result I never check in to see what my needs are.
I am obsessively anticipating your needs.
That is why self care is so freaking hard. Self care becomes dangerous. I think this happens at a very young age.
Most people don't like even a whiff of co-dependent behaviour. They don't like people anticipating their needs. On the other hand... abusers, narcissists, psychopaths, lazy people LOVE co-dependents and need them just as the co-dependent needs them.
