I've been on both ends of this issue.

For me, one of my mistaken core beliefs was that I was broken and fundamentally flawed. It affected my level of confidence, my ability to advocate for myself, my ability to even see that life could ever be different for me. I did learn to finally reject that core belief as in itself flawed, the responsibility of the people who had caused me so much damage very early on in my life. I had to reframe my understanding of my history as what it was -- history. Yes, I had suffered great damage in childhood, but I am not irreparable. I am resiliant, capable of healing, and able to move away from that history, leaving it where it needs to stay -- in the past.

My husband sounds very much as your T described you. I realized finally that he has gaping holes in his life that I will never personally be able to fill, no matter how hard I try, no matter how much he wants me to fill them up. He has to heal the cracks in the bottom of that hole on his own so that what he receives from others doesn't just drain out the bottom. I can't do that for him. He's finally getting there. He's realized that until he changes his belief that no one will ever really love him, he won't truly accept or fully trust in anyone's love for him, no matter how clear the evidence is. He's learning to slow his thinking down. To stop those negative thought spirals that have become habitual for him, and to challenge his own thinking against reality and evidence. He's gotten so much calmer internally, his depression has greatly lifted, his blood pressure has stabilized, etc., and he's learned to relax and enjoy the beauty of relationships instead of defaulting to his old thinking that was so distrustful and almost paranoid. It can be done, but it takes setting boundaries on your own thinking in a way.