Is it possible to cure yourself of addiction, with no outside help?

Anytime someone calls Loveline and says they're trying to quit pot or something way worse, Dr. Drew always responds that he or she will absolutely have to get themselves into a 12 step program AND get a sponsor. He adamantly states that quitting on your own will not work. And the ones that have already enrolled get chastised for not having a sponsor. Says it's just a matter of time before relapse. Is this always true? There has to be some people out there who've quit and stayed that way for life. Is outside motivation always necessary? For example, I'll bet many people have quit drugs cold turkey without problems because their job requires drug testing. Or they got arrested. Dr Drew seems really intelligent, and is an addiction medicine specialist, but is he correct about this one?