What they don't realize is things like going through withdrawal and intense psychological cravings are what cause the addict to use. Then when they experience problems from one drug they try to make themselves feel better by self medication with a different drug causing a new addiction and so on and so forth. For example: when an opiate addict does opiates the endorphins are depleted and certain areas of the brain become over stimulated. So he may take say canal to feel better. Soon he is addicted to benzodiazepines because the gaba receptors are damaged or down regulated. So this person takes more and more benzos and opiates hence having addiction. It's a downward spiral caused by a disease of the brain brought upon by these external substances. It aside from the first decision to use is not a choice at all. This first choice to use is caused by factors such as peer pressure, family problems, and the self medication of mood disorders like anxiety and depression. After the first couple uses, the brain chemistry is already changing and it quickly is out of the addicts control.