It was 1971 and the Vietnam War was heading into its 16th year when two congressmen, Robert Steele from Connecticut and Morgan Murphy from Illinois, made a discovery that stunned the American public.
While visiting the troops in Vietnam, the two congressmen discovered that over 15 percent of U.S. soldiers had developed an addiction to heroin. (Later research, which tested every American soldier in Vietnam for heroin addiction, would reveal that 40 percent of servicemen had tried heroin and nearly 20 percent were addicted.) The discovery shocked the American public and led to a flurry of activity in Washington, which included President Richard Nixon announcing the creation of a new office called The Special Action Office of Drug Abuse Prevention.
The office was created to promote prevention and rehabilitation of drug addictions and also to track and research the paths of addicted servicemen and women when they returned home. It was this last part, the tracking of returning soldiers, that led to some surprising insights.
Lee Robins, one of the researchers in charge of tracking the veterans, found that when the soldiers returned to the United States only 5 percent of them became re-addicted to heroin. In other words, 95 percent eliminated their addiction nearly overnight. 
This finding completely contradicted the patterns of normal addiction. The typical heroin cycle went something like this: an addicted user would enter a clinic and get clean, but once they returned home, the re-addiction rate was 90 percent or higher. Nearly every heroin addict relapsed. The Vietnam soldiers were displaying a pattern that was exactly the opposite.
What was going on here? And, perhaps more important, what can it teach us about changing our own behaviors, building better habits, and breaking bad ones?
How Addictions Get Shaped
Here is what happened in Vietnam: Soldiers spent all day surrounded by a certain environment. They were inundated with the stress of war. They built friendships with fellow soldiers who were heroin users. The end result was that soldiers were surrounded by an environment that had multiple stimuli driving them toward heroin use. It's not hard to imagine how living in a war zone with other heroin users could drive you to try it yourself.
Once each soldier returned to the United States, however, they found themselves in a completely different environment. Not only that, they found themselves in an environment devoid of the stimuli that triggered their heroin use in the first place. Without the stress, the fellow heroin users, and the environmental factors to trigger their addiction, many soldiers found it easier to quit.
Compare this situation to that of a typical drug user. The individual picks up a bad habit at home, goes to a clinic to get clean (e.g., somewhere devoid of all the external stimuli that drive their habit), then return to their old environment with all of their old triggers surrounding them, and somehow hope to quit their bad habit. It's no wonder 90 percent of typical heroin users became re-addicted once they return home -- they are surrounded by all of the things that caused them to get addicted in the first place.
Similar situations drive bad habits for all of us, from nail biting to smoking to drug use. Of course, none of this is to say that the change in drug use was purely due to environment changes. (It is likely there were a variety of factors at play. [2: There is an additional caveat to the Vietnam study that I believe is worth mentioning. The percentage of soldiers who remained addicted after returning to the U.S. was very similar to the percentage of addicts we typically find in society. I'm not an expert on addiction and can't say what the answer is, but it's obvious that environment change is not a magic cure to all addiction problems. It is best to view this simply as another tool in your tool belt that you can use to build new habits and break old ones. As always, the only truth for you as an individual will be what works for your life, so embrace an attitude of self-experimentation and try things out to see what works for you.]) But the central idea is a solid one: The stimuli that surround you shape your behaviors day after day, often without you realizing it. Environment drives behavior.
To Change Your Behavior, Change Your Environment
The impact that external stimuli can have on behavior is well-known. I have written previously about choice architecture and how it can be used to drive better health habits.
These effects go beyond the physical environment. Your friendships matter too. One popular study, published in the New England Journal of Medicine, tracked 12,067 people for 32 years and found that "a person's chances of becoming obese increased by 57 percent if he or she had a friend who became obese."  The people we connect with and the places we live in often determine our behavior and habits as much as we do ourselves.
The good news is that, at least to a certain degree, your environment is within your control. If you want to change your behavior, then change your environment. Even small adjustments can make a difference. One of the simplest ways to do this is to "design for laziness" and make default options healthier or more productive, which is a strategy I covered in detail here.
Here are some other examples to get your creative juices flowing:
Trying to build an exercise habit? Rather than going home after work, stop by a new place like a park or a hiking trail (or a gym, if that's your thing), and let the new environment be a blank slate for your new behavior rather than trying to force yourself to overcome all of the old triggers at your home.
Want to think more creatively? Move to a bigger room or surround yourself with expansive architecture away from the normal space that drives most of your thought patterns. (More on the link between architecture and behavior here.)
Hoping to buy healthier food? It is likely that you have some autopilot shopping habits right now. Try going to a new grocery store and developing a different routine of selecting food. You may find it much easier to avoid unhealthy food when your brain doesn't automatically know where it is located. (You can even use my outer ring strategy to avoid most of the processed food.)
By simply removing yourself from an environment that triggers all of your old habits, you can make it easier to break bad habits and build new ones.
James Clear writes at JamesClear.com, where he shares science-based ideas for living a better life and building habits that stick. To get strategies for boosting your mental and physical performance by 10x, join his free newsletter.
This article was originally published on JamesClear.com.
Need help with substance abuse or mental health issues? In the U.S., call 800-662-HELP (4357) for the SAMHSA National Helpline.
For more information on mental health support for veterans, visit http://www.mentalhealth.va.gov/.