One grounding technique (to assist those dealing with overwhelming emotions) is to list 5 things you can see, 4 things you can feel/touch, 3 things you can hear, two things you can smell, and one thing you can taste.

I use this myself when I am trying to stay in control of my emotions and think it could be a great strategy for children.  To help kiddos remember to use the strategy and how to do it, I created a sign that can be printed (get the pdf here.)