We've all seen the videos of the toddler who falls down and depending on what the adult's response is, the toddler will respond similarly. If the adult brushes it off and acts like it's no big deal, the toddler seems to be all right. But if there is a big fuss made over what happened, the toddler may start to fret and cry. What does this mean? 

It means that pain isn't entirely just a response to a physical stimulus. Our environment can influence our experience of pain (the adult's response to the toddler's fall) and so can our emotional state. When we are anxious or fearful about pain, we can experience our pain as out of control, 100 out of 10 pain.

All pain is processed in the brain. That does not mean that your pain isn't real or that you're not experiencing pain. What this tells us, for a lot of chronic pain or symptoms, your brain learned the signal of that symptom and over time, it encoded that signal to mean "pain/symptom" even when structurally there is nothing to cause the pain or symptom. It's an automatic habit that your brain produces when it receives this signal.

There are many things that affect the brain's processing of pain which is why multimodal approaches to chronic pain are necessary. One approach is using Pain Reprocessing Therapy. PRT is mental health treatment that retrains the brain on how to properly understand the signals to help minimize your experience of pain and other physical symptoms.

This is a short video from the Meg Foundation that also explains this mechanism: