Try 10 long (count to 5) slow, deep breaths. Fully fill the lungs, hold, fully exhale, hold, and repeat. While doing th you and this, focus on the sensations inside your lungs to the exclusion of all else.
If this doesn't work well enough, carry a small paper bag with you, and breath into it for a few minutes whenever you need to. This increases the carbon dioxide levels in your blood, which has a very calming effect.
You could also consider getting a companion dog, and have it registered as such, so you can go everywhere with it. I've noticed Labradors, Greyhounds and Wolfhounds are excellent at these jobs. They lean in, demanding affection, when you are emotional, the act of petting them is calming. And, if you wish it, they can attract warm chats with dog-lovers.
Rapid Eye Movement Therapy, formally known as Eye Movement Desensitization and Reprocessing (EMDR), has been proven to be highly effective for PTSD. It helps to read the book written by the person who discovered and researched it, Dr Francine Shapiro -
and then find a therapist who is trained in the method.
If you have nightmares, maybe try some marijuana tea at night. THC helps reduce dreaming and increase sleep. You could add a teaspoon of valerian to the tea - but it tastes disgusting and needs disguising with things like liquorice root, honey and milk.
If you can walk 7 k's a day or do 15 mins interval training on a bike, this also helps to get better sleep. Better sleep means being better able to cope with stress during the day.
