The often-stated notion that people with addictions are "impulsive" goes right along with the myth that addiction is pleasure-seeking or the result of some weakness of the mind. If you believed those myths then you would be willing to believe that addictive behavior is an unthinking, sudden act simply expressing an urge to instantly have what you want. But anyone who has experience with addiction knows that addictive acts are virtually never impulsive.
Addictive behavior occurs at the end of an emotional path, a journey that can take hours or even days. The first step in this journey is having the thought of performing the addiction -- drinking, for example. Moments to hours after having that thought, a person may make the decision to drink. But in between these steps there is often an internal struggle over whether or not to act. Sometimes, during that period the thought of acting seems to disappear or is pushed out of consciousness for a while. Then there is another delay. Even after the decision is made, the act has to be planned. Commonly, people wait to leave work at the end of the day to go get that drink, or have to get in the car and drive to a liquor store or a bar. There is then a wait for the waiter or the bartender to take the order and to have the drink brought over. Delays of this sort are present in every addiction. In compulsive (addictive) gambling, it is often necessary to drive a distance to the closest casino. Where I live it takes about an hour, but compulsive gamblers make that trip all the time. Likewise, there is planning and delay in contacting a drug dealer, or driving to where prostitutes hang out, or finding a time to be away from others to privately get on the Internet to watch porn. I have seen cases in which people with addictions plan their drinking or calling a prostitute or obtaining their drug days in advance. None of this behavior is impulsive.
Real impulsive behavior is immediate. It is simply stimulus-response, like a biological reflex: see it, do it. Since it is literally unthinking, impulsive behavior has no planning. Indeed, if there were a delay or a need to plan the action, people would use their common sense and decide not to do dangerous or destructive acts.
Addictions are almost the opposite of impulsive action. When people with addictions feel an intense drive to eat or drink or gamble or watch pornography, we call such behaviors compulsions. (These psychological compulsions are different from the biological illness "OCD.") These compulsions are triggered by emotional factors and generally represent an attempt to regain a sense of control when people feel helplessly out of control. For example, after a devastating loss people sometimes irrationally clean and straighten up their house, unconsciously trying to re-establish order and control in their lives. In Shakespeare's play Macbeth, Lady Macbeth has a similar compulsion to repetitively wash her hands, to cleanse her of her guilt at having been complicit in several murders (symbolically "wash the blood off her hands"). Compulsions have meaning and purpose and can be understood. They are complex functions of the mind, rather than a simple impulsion to fill an immediate wish. Addictions are compulsions and they, too, are attempts to (temporarily) regain a sense of control when that sense has been lost or taken away. That is why addictions can tolerate delay: it is relieving just to have decided to perform the addictive act, since in making that decision one has already seized a measure of control. This is why it is so common for people to report that once they have decided to drink or gamble or eat, they feel better.
The fact that addictions are not impulsive underscores why they are not essentially a problem of brain chemistry. The "brain disease" chemical model requires that addictive behavior is driven by stimulation of the brain's pleasure pathway. That would fit the facts if people, like the rats on whom the brain disease theory is based, immediately scurried about seeking drugs when stimulated by cues. The rats are seeking pleasure and their response is active so long as their brain chemistry is stimulated. But a brain stimulation model is inconsistent with the delayed, meaningful, non-impulsive nature of addiction.
Knowing that addictions are not impulsive is another reason that people who suffer with addictions should not be seen as pleasure-seeking, weak or unthoughtful. They are just people who, along with all their perfectly good functioning, are troubled by a particular psychological symptom. That means they are pretty much like everyone else.