I think I have experienced a milder version of this sort of attachment when I was younger. I had a hard time getting over a relationship that ended abruptly without closure once, and found myself looking them up too much online or hoping I would run into them. I still get a little extra sad at saying bye, but I have sort of improved in that sense over time. Like, I was sad to move and say bye to my therapist and pdoc, but I feel like I will be okay and am moving forward. For me, I think it was a bit of an attachment issue mixed with my tendency to obsess and ruminate anyway, making it harder to move on. It does seem like a good topic for you to discuss with your therapist (it sounds like you are). Self awareness and cutting myself off from the rumination helps me. I also think realizing what place I wanted that person to fill in my life that might feel empty, perhaps as a result of things from my past, helped. Like, is it really about them? Or is it about this loneliness I have felt that I am trying to fix? Can I get those needs met in a different way? That sort of thing. It's tough, but I think it is possible to learn to manage it.