For me, it relates to the too much/not enough principle. I will be too much for her, I will drive her away. On the other hand...I'm not enough, I'm not worthy of her, my problems aren't big enough, my 'traumas' (my quotes, not hers) aren't enough for me to have the reaction that I'm having and therefore I can't open up fully because I will experience rejection and abandonment again. I actually had the experience you describe - my experience of it, anyway - which was not being able to 'get through' emotionally and subsequently end up abandoned. The boundary she put up was a non-negotiable one and that made me feel so worthless, like my pain and suffering meant nothing because it was just a boundary, I felt she couldn't understand me, wouldn't hear me and if I pushed to get her to understand me it felt like I would have pushed against her boundary. I got through it but it did destroy me (ultimately in a positive way, but it was one of the most painful things I ever went through). I really had to work through the pain, and make a choice as to whether violate her boundaries, essentially, or deal with it. I 'dealt' with it but it wasn't easy. But it made me realise parallels between her behaviour and my mum's and what is triggering to me, and it was healing because it wasn't the same experience and I knew that despite what I was feeling, she was there for me. Edited to say: that's what was different. It replayed the abandonment because the situations were similar but despite feeling abandonment and re-experiencing it, I came out of the other side realising that I wasn't. If that makes any sense at all.
I still haven't even touched on the most horrible stuff. I can't because it feels so painful and shameful but like it is nothing, too. And I don't want her to think that (even though we just argued about trauma where she said pretty much the opposite). But yeah. Trust. It's hard. It is so hard to let that person in when doing it before meant devastation.
