100% agree. This idea can be found in Ken Keyes, Jr.'s A Conscious Person's Guide to Relationships, which is one of my all-time fave books.
I see some truth in this, but I think it's too broad an assumption. I agree with what @AMGT said. I know I can be needy, and there might have been some co-dependency in my marriage, but I'm learning to be alone now, and I don't think that people who can't be alone are incapable of love or of sharing. This hits close to home for me, emotionally, which is why I needed some time to think.
I'll have to think about that.
Please do...