I don't think attachment is painful. I am attached to my pets and I leave them without pining. I am attached to my parent and I only see him once a year or so, I was attached to my person and when she was alive she could go off and live in other countries for a few months and it was not painful - I trusted she would be back. I would not use the word attachment or even bonded to the descriptions I see of people when they talk about the therapist. Those may be in there of course I am not saying there is no element of attachment that can exist alongside these other feelings, but I don't think it is either of those that is the painful sounding longing that I read about.