I withdraw, stare out the window, and shutdown when my stress level goes up. My T just waits for me to re-engage or change the subject.
I usually just focus on my breathing. During really tough topic, I tend to press my car key into my palm. For some reason, this helps. During the exercise I did last session, my T asked me for a funny story or situation. During the exercise she would switch to this topic as kind of a distractor. This seemed to settle me a lot.Then we would start again. Not sure if this is what you are looking for.