This deep breathing technique is at the core of many mindfulness and relaxation practices. It may take a lot of practise to get right, but it is well worth the effort! This calming brain break is suitable for children aged 5-11. Learn what the diaphragm is and how it works. Learn the benefits of deep breathing: Deep breathing activates our parasympathetic nervous system which slows our heart rate and puts us in a state of rest. It's needed for a healthy nervous system and gets us feeling calm and relaxed.