My T used to be the first one to pick up on it but now I do as well. If she doesn't stop and say, "I think you need to just sit with your feelings/your body" etc... first, I will usually say something like, "I think I need to stop talking for a minute and just check in with myself." Breathing always helps as does reminding myself that I am in present day.
Sometimes, if it is really tough, I will ask T to hold my hand.