Can't help you, but wanted to ask for my own benefit, what the DBT course told you to do in such an extremely emotional state?

When I'm in a relaxed and happy mood I'm less prone to get emotional flashbacks. So the easy answer is to don't worry be happy, just that this obviously doesn't work in those unhappy states coming out of nowhere, or when someone is upsetting me and I then overreact before I even know it.