Reservations on drinking and using are things that we cannot afford to have. The literature of AA also calls them "lurking notions". They come in the form of "if this happens then I can drink." "If I get my job, family, and community standing back, and stay sober for a year, I can drink again safely."
In the "Doctors Opinion" of the book "Alcoholics Anonymous" the author (Dr. William Silkworth) describes two classes of people. He talks about people that have the allergy to alcohol and the people who don't have it. Now, if you have it, you keep it. You won't return to or become the person who doesn't have the allergy. He says in his essay that the only answer to the disease of alcoholism is complete abstinance. What that means is that we can't drink no matter how good things may get or how bad things may get. If we take a drink, the craving returns, and we won't stop. Reservations are dangerous. They are deadly.