I have this problem too. My t and i handle it in a couple of different ways. Sometimes, grounding reminders are enough to keep me in the present. At other times, if my emotions seem to be keeping overwhelming and i can't stay present, she will ask me if the hurt (or angry or scared) part of me needs to be put into a safe place so that the adult me can talk about it. (Often that is what needs to happen.) Or if i can, she will have the adult me stay present and picture the dissociating part of me sitting in a different chair and see if i can keep the awareness of both parts and engage in a dialogue between them.