I lay in bed this morning and this thought process went through my head: In order to feel fulfilled, you have to provide a way to be fulfilled. Sitting on your "hope chest" waiting for someone or something to come along and fulfill you, will leave you unfulfilled and depressed. But getting up and figuring out what it is you need in utter to feel fulfilled will usually get the job done.
Dogs will find a way to fulfill themselves, whether their owners provide the needed stimuli or not. If not, their fulfillment usually comes through unwanted, naughty behaviors and destruction of property, people and other animals. If their needs are met and they feel fulfilled, there is only room for contentment and belly rubs.