Alcoholism is a progressive disease, meaning it gets worse with time.
As time goes on the individual must drink more and more to get to a certain point of numbness. It is hard for the individual to quit after one drink. The middle stage is when the alcoholic begins drinking on a daily basis. As a result of having to drink more and more to achieve the same state of numbness, tolerance increases and the individual begins to become dependant. This is when the alcoholic is hides drinking, and drinks alone.