If you read some of the stories in the books and websites listed under resources in Part 1 you might come across some anecdotes which illustrate this process. I paraphrase:
A Viet Nam veteran who was injured in the leg during an incident involving a helicopter recovered fully from the injury. However, periodically over the years he would suddenly experience intense pain in the previously-injured leg which would last for several days before dissipating. One day his wife commented on the helicopter flying overhead and it dawned on him that every time he heard a helicopter's engine his leg hurt.
One lady experienced intense pain whenever she drove through a particular town. She eventually realized that the town was en route to the in-laws' home where she often felt the same pain because of the stressful atmosphere. In time she experienced the pain when travelling that route even when not visiting the family.
Have you every taken an instant dislike to someone whom you have never met before and wondered why? Perhaps he or she reminds you of someone with whom you have previously had a bad experience. Have you ever had memories flood back instantly transporting you in your mind's eye to someplace else in response to a song, fragrance, or scenery? This is because the parts of the brain involved with memory, pleasure and emotion are very closely associated, and are also connected to the parts of the brain which process the flight and fight response. The limbic system is also closely connected to the thalamus which is the clearing house for the processing of painful stimuli.
One of the questions I have learned to ask patients with unexplained pain is: "What was going on in your life when it first happened?" This sometimes gives a clue as to the meaning of the pain and how to approach it.