In kindergarten our students haven been learning about how to calm down when they have strong feelings. Belly breathing (diaphragmatic breathing) helps lower blood pressure and heart rate, which calms the body. Conversely, noisy, fast breathing and breathing from the chest can cause students to feel more upset. It is very important to model the correct technique for belly breathing and then to coach students to do so also.
Below is a great video with Elmo that explains how to belly breathe: