You eat sugar, carbohydrates, fruits... and you drink orange juice and cola. The sugar level in your blood rises. Your brain detect that increment and order to insulin to convert sugar in fat....and you create a «wonderful» belly, ready to fuel energy in the future. Same with bad, dangerous, threating emotions. Lots of situations, experiences and circumstances in your life overflow your mind with sadness, anger, hate, rage, frustration,... When the sum of that «negative» emotions gets certain «level of security» our protective brain activates the «repression mechanism»: all the excess of new bad emotions will be diverted to some kind of «subconscious reservoire». If the input of that negative emotions doesn't cease the pression of the subconscious reservoire rises and rises. Pain is the main way for avoiding the explosion of that reservoire. Some kind of valve of security. Debatable, as many metaphors...but instructive, I hope.