Whether it's your fourth cookie, shoe purchase, or cigarette, it's common to pass off a moment of weak willpower as being caused by an addictive personality. But according to research, there's no such thing.
Sure, there are personality traits that are associated with addictive behavior: neuroticism, for example, or impulsiveness. But those are just traits. Just because scientific evidence shows that most people with addictions are neurotic doesn't mean that neuroticism makes you prone to addiction—there are plenty of neurotic people who aren't addicted to anything. Likewise, research shows that having one addiction makes you more likely to have another, but plenty of addicts stick to a single vice. Different vices also fulfill different personal needs for different people: we've all heard of the depressed alcoholic who drinks to numb the pain and the party-animal alcoholic who drinks to make life more exciting. Same drug, two different personalities.