You've done it again. Another Christmas season of too much food, too much wine, too much partying. It was fun at the time, but now, in your annual tradition of self-disgust, you swear never again. Come Jan. 1, you resolve to go on a rigid diet, to have one martini a year, to exercise an hour a day and to be asleep every night by 10.

Don't bother. Rough resolutions like this are doomed to fail, and then you'll just feel surly again -- and probably blame yourself for failing instead of blaming your impossible goals. In fact, most New Year's resolutions are so rigid and ruthless that they might do you more harm than good even if you could stick to them -- which is unlikely.

But there are ways to change your life effectively and even reasonably. The key is to acknowledge Aristotle's Golden Mean, as translated by your family doctor: All things are fine in moderation. Even excess is fine in moderation, such as a holiday feast or Mardi Gras blowout.

The problem with New Year's resolutions stems from the faulty assumption, prevalent in our culture, that the answer to overindulgence is abstinence. Drinking too much? You'd better quit entirely. Eating too much chocolate? You must never eat chocolate again. Not exercising? Better run six miles every day.

This all-or-nothing style sets you up for binge cycles and broken vows. Most people cannot -- or don't want to -- abstain entirely from the foods, drinks or activities they enjoy. When they try, they become even more attracted to the now-forbidden fruit. Then when they fail, as fail they almost always do, they say, "Aw, what the hell, I blew it" -- and a binge is born.

There's also the danger of going too far in the "healthy" direction and becoming a fitness fanatic. Most of us tend to worry about the dangers of too much eating and drinking. But there are many people who over-exercise, or diet obsessively and without pleasure -- excesses that can be just as unhealthy.

In my research on addiction (to a wide variety of substances and experiences), I find that the vast majority of people employ moderation most of the time. Only a steady minority, about 10 percent, abuse a substance or activity, making it the focus of their lives. It almost doesn't matter what the substance or experience is: Alcohol. Cocaine. Heroin. Jogging. Sex. Tranquilizers. Food. In each case, moderate users keep the activity within bounds. This is true even for heroin users, as revealed in Harvard psychiatrist Norman Zinberg's recent book, "Drug, Set and Setting" (Yale University Press, $22.50).

Smoking may be an exception to this rule. Of course, smoking even small amounts of tobacco is not healthy. Total abstinence -- cold turkey -- is probably the best way for most people to defeat a smoking habit.

However, Stanley Schachter, a Columbia University psychologist, found that smokers may sample a cigarette at a party without going all the way back to their former habits. And some individuals are able to cut heavy smoking down to a fixed, small allotment. Comedian Sid Caesar, who used to smoke 10 to 15 cigars a day, now smokes only two a day.

"I would light cigar after cigar and not even enjoy them," he remembers. "Now, because I smoke cigars so sparingly, I really look forward to it and get pleasure from them."

Tobacco aside, abstinence is often a poor way to change a habit. The reason is that abstinence makes the heart grow fonder of the thing it no longer has -- and a relapse often results.

For example, most alcoholism treatment programs in the United States try to turn heavy drinkers into teetotalers. But as British psychiatrist Griffith Edwards observes, "Total abstinence may result in patients alternating sobriety with explosive relapses."

Because the relapse rate for abstinence methods is so high, psychologists have now developed several moderate-drinking programs for problem drinkers. They teach clients how to sip drinks instead of gulping them down, how to monitor their blood-alcohol levels and how to refuse a drink. William Miller, a psychologist at the University of New Mexico, has found that in 21 of 22 studies, moderate drinking methods have produced positive results.

While it's true that for some alcoholics the option of moderation is no longer workable, the resolution never to have a drink again is not always a cure-all.

The vast majority of alcoholics who try to abstain eventually return to the bottle or turn to another addiction. Dr. George Vaillant, in his book "The Natural History of Alcoholism" (Harvard University Press, $25), found that 50 percent of abstaining alcoholics formed intense dependencies -- on eating candy, praying or other activities. (Those who simply reduced their drinking didn't become dependent on other things.)

The same problems apply to strict dieting. Toronto psychologists Janet Polivy and Peter Herman, in their book "Breaking the Diet Habit" (Basic Books, $16.50), show that those who severely restrain their eating, who are obsessed with counting calories, are most likely to have outbursts of gluttony. The strict dieter who slips and has a single rich dessert often goes on to a binge. (Bulimics, who follow their binges with self-induced vomiting, are an extreme form of this inability to steer a stable dietary course.) And dieters, too, may replace food with alternate compulsions, such as an addiction to running.

What about drugs? Actually, most drug users are occasional, social, moderate users; only a minority become full-fledged addicts. According to Zinberg, the policy of trying to discourage and punish all drug users has failed utterly, and actually backfires in two ways: It makes the drugs forbidden and therefore even more attractive, and it makes it harder for users to learn moderate ways of using the drug. Certainly, none of our prohibitions have solved the drug abuse problem.

It's all very well and good to advise moderation, but how do we get there from here, moaning on New Year's Day? The therapies that are successful in teaching moderation take several factors into account: what you do, what you think about what you do and what your environment encourages or suppresses. Self-imposed New Year's resolutions concentrate on only the first ("I won't do that anymore"). But to carry out that resolution, people need to change their attitudes as well, and to make sure their friends, relatives and colleagues support their desire to change.

In a world that rewards excess and preaches abstinence, choosing the middle route of moderation isn't always easy. But if you do, you'll be able to eat (some of) your cake -- and have it, too.