That this is necessarily so can be seen by examining the population prevalence rates of current and former users, the rates of change in these behaviours over time within a general population, and the relatively small number of people who receive formal treatment for these problems.
Most people who quit smoking do so on their own with no formal help. Most people who have problems with alcohol are found, years later, to have solved or reduced their problems, and only a small minority of these do so with the help of treatment. How do such changes occur? When self-changers are asked why and how they did it, they commonly reply that they just decided to.
Some describe specific events that shocked them, and caused them to see themselves and their habit in a new light.
Some relate religious experiences, interactions with family and friends, or life transitions as triggers for their change. In many cases, however, there is a common set of decision running through the stories of self-changers. Things may have happened around them, but something also happened inside them to set off a change.
The crucial point to remember is that the decision is the essential part of every change.