An addiction is a pattern, a pattern of self-destructive behavior. How does it begin? Maybe a person is in a bad experience and they happen to do something that distracts them---when the next difficult experience comes along, they think of doing that distracting thing again. Or, maybe the person is actually having a bad time with themselves; whatever triggered it, their state of mind is one they don't like. They remember something they did previously that altered their state of mind and so they think to try that again.
It begins as an attempt to address a problem of some sort, becomes a habit and turns into an addiction. Unfortunately, once it becomes a habit, the individual has already begun to cripple themselves. Grappling with conundrums, dealing with dilemmas, and wrestling with problems is a learning process. We do become better at problem-solving as we practice.
It isn't only collecting experiences to draw out of memory, but, also, learning problem-solving processes, figuring out how to deal with the attendant emotions and still be able to think through something, and, discovering what works best for the individual. When one indulges in the habit of avoidance, which is a way of referring to addictive behaviors, one robs themselves of this learning process. Some theorists go so far as to say this: An alcoholic's development is arrested at the time they began drinking alcoholically. In other words, all maturing is interrupted. So, for example, if you know a 43 year old man who seems to function like a 16 year old, perhaps he has a substance abuse problem.
Addictions can appear in so many forms, sexual compulsivity, a gambling addiction, workoholism, prescription drug abuse, compulsive overeating, and addiction to pornography, to name some. It is something that can happen to anyone. The sad irony is that any addiction was begun as an attempt to make things right in some way. Of course, it ends up undermining all of life, even the parts that were good. Also, there is usually collateral damage---that is, people in close relationships with the addict find themselves in pain.
If you find yourself turning to a chemical or unrelated activity when you feel any way that you don't like or when you are in the midst of a challenging or distressing life event, take notice. It is usually better to struggle through the difficulty without alteration or distraction.