The actual act of quitting anything is easy, once the person has convinced themselves they have the power. For many wioth substance abuse issues, however, the reason they adopted bad habits was as a result of exchanging a weakness for a comfort. Giving up self-taught comforts, based in self-indulgance. oft requires a tragic or otherwise shocking event to occur.
Breaking old habits of diet, i.e., eating foods having artificial colors, flavors, canola oil, hydrogenated oils, fluoride, alloxan, etc. requires more effort than withdrawing from a barbiturate habit.