Please first look at Step 4 Understanding Pain if you have not already done so.

Our bodies are constantly sending information to the brain, including pain information. If you sit in one position for over 20 minutes, sensors in your muscles send messages of alarm to your brain. 70% of us don’t feel that pain.
The messages pass through the alarm system of the brain, the Limbic System, and from the limbic system, the messages go to other parts of your brain, including the thinking part of your brain, the cerebral cortex. The thinking part of your brain recognizes you are not in danger and it simply deals with the issue. The thinking part of your brain – the cerebral cortex – will send a message to your body to move. You might make a small adjustment in your posture, or, your body may ignore the message and you don’t notice the pain because your body is not in a state of alarm. (You may pay for it later, if you do not pay attention, usually, with neck and back pain.)
30% of people – the people who suffer with chronic pain, will feel most or all the messages sent to the brain. The more active your alarm centre in the brain is, the more pain you will feel.
On a good day, your pain can feel better. When you are having a particularly stressful day, your pain will feel worse.
Chronic pain is difficult to treat and can often not be cured. This causes stress which activates your stress centre. See below what that does to your body.
Many patients feel as if they or their doctors have failed. This causes more stress which changes your body and causes more pain.
Perhaps one day we will be able to cure all pain, but today, even with the strongest pain medication, we can often count ourselves lucky if we improve pain, rather than remove it completely.
Fear, anticipation of pain and generalized anxiety make pain worse. And it’s not all in your head. Hormonal changes alter how your body functions. See below

Unfortunately certain parts of your brain do not recognize the difference between physical and emotional stress, not even the difference between good and bad stress.
Hormonal changes in your body respond to stress to protect your body in the event of a catastrophic failure, like blood loss from trauma. Adrenaline and Noradrenaline released raise blood pressure and heart rate. Eventually your cortisone also goes up. Even anti-diuretic hormone can rise causing swelling.
These changes wreak havoc on your body. This combined with chronic pain places your body at risk.
Learning how to manage stress, anxiety and depression is very important. Your mental health has to be stronger than a person who doesn’t struggle with pain.
Use any and every resource that you can to improve your mental health.
Take a look at the help section.