The dog vigilantly protected his bone, although it was dry and hard.  It really offered no real nourishment to the dog.  However, he brought it out and chewed on it each day, something to pass the time.  It offered hours and hours of chewing pleasure to the dog until eventually it wore down.  Soon thereafter, he got another bone which was just as dry and hard.

Like the dog's bone, anger is hard, dry and without nourishment.  Whenever we continue to gnaw upon the bones of misunderstanding, a habit grows until the harboring of a problem becomes a regular pastime.  We can actually become so dependent on negative feelings that even when given an opportunity we would rather seek a replacement (to continue in anger) than a solution.