The drug and alcohol addicts are prisoners of their own self destruction. And they themselves are to blame for letting themselves become drug and alcohol abusers.
The Beast is the "Drug and Alcohol Addiction" an addict will have to live with for the rest of their lives.
The addict will never be rid of the addiction. It will be a constant battle for the rest of their lives to live drug and alcohol free.
You can check out anytime you like but you can never leave refers to "Once an addict always an addict!"
I hope this help those who were always confused by the songs lyrics...Peace!