The mistress could be a metaphor for drugs. For drug users, the substance is a lover/mistress because their lives revolve around it. First, there is the "honeymoon," where the user finds comfort in it. Soon enough, the consequences of drug abuse show up. It is "a nightmare from which (he) cannot awaken." The mistress has become an enemy, it "takes away everything": job, money, home, health ("weakened as I am"), relationship, friends, etc. Even if the user contemplates quitting, he lives for their next dose ("just give me another moment from which I will never awaken"), and for those who manage to quit, relapse is common, sometimes replacing a drug for another, such as injecting cocaine instead of heroin ("falling again for another mistress of burden to idolize").
Sophie - Montreal, Canada