People in chronic pain are often advised to take a deep breath to help them relax. We are often advised to take deep breaths but never told that it isn't the breathing in that is beneficial but the breathing out.
It is only when you exhale that you release tensions. Most people in chronic pain do a lot of breathing in but barely breathe out at all. If you are in chronic pain you need to focus on your exhalations. Make your out breath long, slow and controlled and focus on relaxing downwards all the time. You may find this very difficult to do at first but do persevere as it will release so much of the tension that is preventing you from releasing your pain.
I run a small business teaching people in chronic pain how to release their pain and tensions through their breathing and posture. I have taught this fundamental breathing skill to a great many people in chronic pain and it is always effective.