I like how they address this question here BTY....This made sense to me.

Why does he behave like this? If hundreds of experiences have shown him that one drink means another debacle with all its attendant suffering and humiliation, why is it he takes that one drink? Why can't he stay on the water wagon? What has become of the common sense and will power that he still sometimes displays with respect to other matters?

Perhaps there never will be a full answer to these questions. Opinions vary considerably as to why the alcoholic reacts differently from normal people. We are not sure why, once a certain point is reached, little can be done for him. We cannot answer the riddle.

We know that while the alcoholic keeps away from drink, as he may do for months or years, he reacts much like other men. We are equally positive that once he takes any alcohol whatever into his system, something happens, both in the bodily and mental sense, which makes it virtually impossible for him to stop. The experience of any alcoholic will abundantly confirm this.

These observations would be academic and pointless if our friend never took the first drink, thereby setting the terrible cycle in motion. Therefore, the main problem of the alcoholic centers in his mind, rather than in his body. If you ask him why he started on that last bender, the chances are he will offer you any one of a hundred alibis. Sometimes these excuses have a certain plausibility, but none of them really makes sense in the light of the havoc an alcoholic's drinking bout creates. They sound like the philosophy of the man who, having a headache, beats himself on the head with a hammer so that he can't feel the ache. If you draw this fallacious reasoning to the attention of an alcoholic, he will laugh it off, or become irritated and refuse to talk.

Once in a while he may tell the truth. And the truth, strange to say, is usually that he has no more idea why he took that first drink than you have. Some drinkers have excuses with which they are satisfied part of the time. But in their hearts they really do not know why they do it. Once this malady has a real hold, they are a baffled lot. There is the obsession that somehow, someday, they will beat the game. But they often suspect they are down for the count.

How true this is, few realize. In a vague way their families and friends sense that these drinkers are abnormal, but everybody hopefully awaits the day when the sufferer will rouse himself from his lethargy and assert his power of will.

The tragic truth is that if the man be a real alcoholic, the happy day may not arrive. He has lost control. At a certain point in the drinking of every alcoholic, he passes into a state where the most powerful desire to stop drinking is of absolutely no avail. This tragic situation has already arrived in practically every case long before it is suspected.

The fact is that most alcoholics, for reasons yet obscure, have lost the power of choice in drink. Our so-called will power becomes practically nonexistent. We are unable, at certain times, to bring into our consciousness with sufficient force the memory of the suffering and humiliation of even a week or a month ago. We are without defense against the first drink.

The almost certain consequences that follow taking even a glass of beer do not crowd into the mind to deter us. If these thoughts occur, they are hazy and readily supplanted with the old threadbare idea that this time we shall handle ourselves like other people. There is a complete failure of the kind of defense that keeps one from putting his hand on a hot stove.

The alcoholic may say to himself in the most casual way, "It won't burn me this time, so here's how!" Or perhaps he doesn't think at all. How often have some of us begun to drink in this nonchalant way, and after the third or fourth, pounded on the bar and said to ourselves, "For God's sake, how did I ever get started again?" Only to have that thought supplanted by "Well, I'll stop with the sixth drink." Or "What's the use anyhow?"

When this sort of thinking is fully established in an individual with alcoholic tendencies, he has probably placed himself beyond human aid, and unless locked up, may die or go permanently insane. These stark and ugly facts have been confirmed by legions of alcoholics throughout history. But for the grace of God, there would have been thousands more convincing demonstrations. So many want to stop but cannot.

BB Pgs 22 - 25