I remember as a parent the first time the therapist talked with my about my child being dysregulated and thought "What the heck does that mean?" If you think of the thermostat on the wall at your house, and the way it regulated the temperature. Only this is about mood.
If our child is regulated, it means they are able to control their emotions, control their bodies. If they are dysregulated they are more than likely having a rage, throwing things, kicking things, yelling, blaming, out of control of themselves.
BUT, here is the hard part. In order to help them learn to regulate themselves, we must first regulate ourselves. Ouch. If it is so hard for us, how can we doubt how difficult it is for them?
Breath deep, it slows down your heart rate and sends oxygen to the brain. Heaven knows mine can use all the oygen it can get! This means your stomach goes in an out when you breath, not shoulders up and down. Oh and put those shoulders back so the lungs can really fill.
Give yourself a time out. It is ok (good even) to say "Mom needs a few minutes and I'll talk to you about this later". Then lock yourself in your bathroom, bedroom, office, whatever and read a magazine, listen to a favorite song, pray, call a friend or spouse. When you are calm, then you can talk.
Make a play date with a friend. Even if you can't go then, knowing you will be "going out for coffee, going shopping, running with a friend" all will help. You can say to yourself. I can handle this because I'm gong to go have fun later.
Exercise. It produces endorphins, burns off anger and is good for you. It's better than eating another snack. It is a social thing for me. At first, yes, it will make you tired. Keep after it and eventually it will give you a ton of energy.
So....regulate yourself first, and then your child.
You've got this.