You know I think the need to be held and soothed in the middle of an awful, unattractive, messy screaming tantrum can persist beyond early childhood. Especially if you didnt get the comfort and holding and reassurance you needed as a small child. You crave that kind of comfort and unconditional love so much and you want someone calm and stable and authoritative to make it okay while you are at your most freaked out. You need to show them just how very, very distraught you are and you want them to witness your pain and have it be okay. That's the test: you see me losing it and threatening to hurt myself, can you still give me love and comfort?
But acting out this way will inevitably leave you feeling worse and feeling betrayed by your T. Because while T can probably handle all those horrible messy feelings, she cannot gently take the razor from you, scoop you up and snuggle you and tell you that it's okay to be upset and she's there for you and it will be okay and please tell her with your words not your hands how you are feeling. You can grow and heal and feel more stable but you will need to mourn the fact that you can't get that exact kind of firm, physical, gentle, soothing love that parents need to give their little children.
There are some ways in which your T can provide you with the "parenting" you need and others in which, sadly, she cannot. It'll just have to be enough to talk about it and cry and curl up into a ball and tell her how awful you feel. And you know, if you stick with it and work on it and commit to your wellness and keep thinking about who you eventually want to be--it probably will be enough.