When there is a real emotional window between me and another person, and especially with a therapist, I become terrified.
For me attachment includes an element of dependence and letting ourselves be vulnerable. I start to need the person in a certain way, so I would miss them and feel something lacking if I stopped seeing them.
Is it the idea of dependence and vulnerability that's so terrifying?
My therapist of three years ago was the first person I'd let myself get attached to, then I was forced to stop seeing her (it was through a charity - there was a time limit on the therapy, and the rules said I couldn't continue to see her in any setting after that). It was terrible, but I did get over it in time and with hindsight I'd still do the same all over again. I'm starting to understand the saying "It's better to have loved and lost, than never to have loved at all". What I got from the trust and the attachment has stayed with me, while the pain and loss of the separation has now gone... thankfully. And the experience of having that before has helped me to work on building trust with my new therapist.
There's also the feeling of vulnerability at the time. I've always had to be very independent and protective of myself, so it went against all that to open up to someone.
I really think the only way through this is to do it, a tiny bit at a time. I don't see any way to think yourself through it, because ultimately you would be trying to reason with a part of you that isn't really acting from reason but from long held fears and habits. I think you need to experience that it's OK, by approaching it in a careful, controlled way.
I think it's a mistake to try to do it overnight, or in a few sessions. Not least because you need to check that this really is a person you can trust, before you give them all the trust you have. But also because you need to pace yourself, monitor the effect, and practise using your coping skills if there's emotional fallout afterwards.
I see the best approach for anyone is first to make sure they've got a toolkit of coping skills and ways to look after themselves when upset. I think we have to be realistic about this - we have to expect reactions that we will have to cope with. Therapists can't do it all for us. And we can't just expect things to magically change because we're in therapy. If we had poor or overly-defensive coping skills before, we will still have those unless we learn and practise new ones.
Then I think you need to try going a tiny bit beyond your comfort zone and wait to see how it feels. For me that has been saying one thing that feels very personal that I wouldn't normally say to anyone - for example, saying how much I was drinking, or that I don't feel any love for a family member, or how depressed I am. Not going into details, telling the whole history, speculating about why or explaining when and where - just a tiny bit. Then going away, taking care of myself and watching to see whether the sky falls down on my head as a result of what I said. Then going back to talk about how much it did and how I coped with that.
If you managed that, and your therapist's reaction felt understanding and supportive, then it's safe to try a little more. And then just keep doing it. Do a tiny bit, wait, listen to your therapist's response, monitor the effect on you, use coping skills, go back and talk to your therapist about how it felt.
If you start doing it, in tiny steps, you'll get somewhere over time. Or - worst case scenario - you'll realise that the therapist's approach isn't for you and you need to find someone else, before you invest too much of your money, effort, emotions and trust.
If you feel you have to go from zero to trust in one go, then I think it would inevitably be too overwhelming. If you try to think your way through it, my opinion is that won't take you forward very easily. I understand that there are theories about attachment, but in the end you're not living theoretically. I think basically you need to push yourself to do something, but to do that wisely.