Even after an addict is cured of his physical dependence on a drug, he remains psychologically dependent on it. As drug use increases, the tolerance level develops. This means that larger quantities of a drug are needed to maintain the same 'high'. Soon the addict feels that he cannot survive without the drug as he will suffer from the unbearable pangs of withdrawal. This is when the addict's life turns into a vicious cycle of desperate attempts to get drugs for his next fix to avoid the withdrawal symptoms.
Drug addicts start out on their drug habit for various reasons.
Some turn to drugs out of curiosity, just to feel what it is like. Unfortunately, they do not realise that they can get hooked even if it is only once. It is one time too many. By the time they find out, they have reached the stage where they cannot stop themselves from continuing their drug habit. Others may be influenced by friends into taking drugs.