The following equation may sound a little strange, but it makes sense to better understand pain. You can compare pain to a dog living in your brain. (If you don't like dogs, you can take another animal!). Like you have 'an inner dog'.
At first glance, pain and hunger seem to have little to do with each other. If you look further, there are many similarities! Getting to know these kinds of comparisons makes it easier to see how you can positively influence your pain.
If something's hard to predict, it's long-lasting pain. Mostly pain that has lasted longer than three months. One day you can exert yourself well and it doesn't seem to worsen the pain, the next day you can't do anything.