Breathing exercises are a key skill for coping with any kind of dysregulation. Slowing the pace of your breath down allows you to consciously influence the state of your nervous system to bring your levels of stress down (or up) so they are moderate. For all therapeutic change stress levels need to be at a moderate level of intensity (not too much, not too little).
Making your exhales longer than usual each time you breathe out is another tip because the part of your nervous system that calms the stress response down (called the parasympathetic nervous system) is active when you exhale. Here is an exercise you can do to get you started.
Disclaimer: All tips and exercises provided are for educational purposes only. Remember to consult with your medical doctor before doing this or any of the exercises. Do not drive or operate machinery while doing this or any exercises.