There are many different reasons why someone might not be able to stop using drugs and alcohol. First, I think that you might have to ask yourself if you are addicted or not. There are two types of addiction really. You can either be addicted psychically, or mentally. Marijuana is known as a drug in which you can not get psychically addicted to, it is more of a mental addiction. From my experience and research, I've come to believe that a mental addiction is far more easy to overcome than a psychical addiction. Herion is known to be psychically addicting, as well as mentally addicting, making it that much harder to overcome and stop using. Being psychically addicted to a drug means that you will become very ill once you discontinue use of that drug. This illness is commonly known as detoxing. Depending on the drug you are addicted to, the length of the detox can vary. Heroin's detoxification usually last from five to seven days long. Where as methadone, a synthetic opiod, usually used to treat heroin addicts in a maintenance program and is prescribed by a doctor, has a detoxification period that can last from one month to 60 days long! Benzodiazipines, and Alcohol are the most dangerous of drugs to stop sudden without being medically monitored because the detoxification can be so intense, it will often lead to siezures, hallucinations, and in some cases death, if not treated correctly. So, if you can admit that you are addicted, then you are well on your way, and one step closer to being able to stop using drugs and alcohol. Another factor why you might not be able to stop using the drugs and alcohol, whicever ones you might be taking, is that it could be herititary. You might carry a gene in which you are susceptible to addiction. This is in no way your own fault, it is just the way that you were born, and you should not feel bad about this at all. It is said that addiction is a disease, and it is nothing you should be ashamed of. it is just as much a disease as cancer, or hepatitis. Another reason that you might not be able to stop using drugs and alcohol is what I believe to be the most common reason as to why is that if you seriously do not want to change, then you won't. It is often said that someone must reach their rock bottom in order to want to change their lives and stop using drugs and alcohol completly. It goes without saying, if you dont want to change, then you most likely will not change, and will probably just continue to use drugs and alcohol. One thing that i can tell you based on my experience is that you cannot change and stop using drugs and alcohol for anyobody else but youself. It will definitley not work if you try to get clean for your parents, your girlfirend, your kids, your siblings, or anyone else for that matter. The only way that you are going to get clean and stop using the drugs and alcohol is if you do it for yourself and yourslef only and nobody else, but you got to actually truly want to stop using drugs and become clean and sober, or else you will just continue to keep on using.