I've mentioned St. Louis U. philosopher Dan Haybron a couple times before. His is the best stuff on happiness in the contemporary philosophical literature. And I'm almost a little bit disappointed that I agree with his position on the nature of happiness as thoroughly as I do. Haybron rejects both the hedonic and life satisfaction conceptions of happiness in favor of a what he calls the “emotional state” view, by which he means that happiness is a kind of steady, pervasive set of dispositions to feel positively. The opposite of happiness is depression, chronic anxiety, or melancholy. (Here is Haybron's paper on the emotional state view. [pdf] Don't trust my characterization. If I am ever creative, it is because I excel at unconscious opportunistic reinterpretation.)
On this sort of view, a person who has undergone surgery and is in terrific pain for a long period of time might still be happy. In this kind of case, the steady disposition to feel good simply isn't realized, but it's still there. And there is no reason to believe that people's judgments about their lives will closely track this kind of pervasive emotional condition. A happy person who has suffered a serious setback in life may say that things aren't going well, but that may leave her deep, underlying affective dispositions unaffected.
This is me riffing now, not Haybron. I think part of what happiness in this sense involves is asymmetry in speed of adaptation. Seligman in Authentic Happiness remarks that the emotions aren't at all like Freud had it. They don't build pressure, and failing to “let it out” won't cause you to blow a gasket (“bottle up and explode!”) or transmogrify the emotion through a kind of emotional alchemy into some other perverted form. Emotions are more like balloons with a semi-porous membrane. They fill with the air of the emotion—the emotional bladder fills with rage or grief—but, absent new infusions, the emotion just seeps away and the balloon deflates. Expressing the emotion dramatically, or rehearsing it over and over in thought or conversation can just keep the feeling inflated and alive. This is why grief therapy can be bad for you. And why a tendency to nurse grievances is detrimental to happiness.
A dispositionally happy person might be thought of as somebody whose negative emotions deflate quickly and whose positive emotions deflate slowly. There can also be complex relations between positive and negative emotions. There are people whose positive emotions deflate whenever a negative emotion is inflated, or vice versa. And there are people who sustain positive emotions, even when certain negative emotions loom large. The happiest type might be the those for whom strong positive emotions tend to deflate negative ones, but for whom stong negative emotions cannot fully deflate positive ones.
Now, happy people in this sense ought to rate high on hedonism and life satisfaction scales. People disposed to feel good longer and more often, and feel bad shorter and less, or to feel good in some way even when feeling bad in others, will on average feel better. And people who on average feel better will likely say they do. But the symptoms of the condition shouldn't be confused for condition itself.
Now, I don't think it's all about pattens of emotional inflation and deflation. There's also a matter of “default tone”—how you feel when there's nothing special going on, when the surface of your emotional seas are glassy.
Note that all sorts of combinations of emotional inflation-deflation patterns and default tone are hedonically equivalent. But all of them aren't happiness. I think happiness has something to do with a relatively smooth hedonic flow. A fairly negative default tone with frequent, huge, euphoric positive upswings and slow deflation back to default may register more total hedons than a mildly positive default tone with mild upswings and mild downswings. But the first well might be a case of bipolar disorder and require serious professional medical attention. That's not happiness, no matter how huge the hedonic payoff of the upswing. My sense is that a lot of Westeners resist the ideals of Buddhism because we think it takes hedonic smoothing too far. Buddhism asks you to trade almost all hedonic volatility for a better default tone.
Actually, happiness-as-condition framework explains a couple different things you might get out of a serious practice of Eastern mindfulness, and why it has bigger returns for some than others. If you have a good default tone, but suffer from frequent or large negative spikes—you're quick to anger, easily frustrated, often indignant, etc.—a practice of mindfulness that simply leaves you at the default tone more of the time will be big improvement. This is the kind of person who says, “Meditation saved my marriage!” However, if you've got good default tone, mild, or quickly deflating downswings, and big or slowly deflating upswings, then a practice of mindfulness will mostly be taking the tops off good experiences. Why do that, as long as you're not manic?
I think Americans who worry about oversmoothing may find mindfulness more useful in controlling rates of deflation than controlling the distance of peaks from the baseline. In my very limited experience, this is what I like about it. You can willfully distance yourself from negative emotions, and deflate back to default tone faster, or engage mindfully with positive emotions, and deflate more slowly. If that pattern became a habit, part of your ongoing emotional condition, you'd be happier person.
The other main reason you might not like either a smoothing strategy (inflation volume strategy) or a deflation rate strategy is that you are accustomed to deploying negative emotions to control other people, ala Griffiths' Machiavellian emotions theory. Emotions aren't just appraisals (immediate internal reports on how well you're doing relative to your goals, values, etc.), they're strategic tools for manipulating other people—for exacting commitment, compliance, concessions, regret, solidarity, affection, etc., etc. If your emotional social management strategy relies heavily on anger, sulking, disdain, guilt-tripping, etc., then a therapeutic practice that shortens the intensity or duration of negative emotions may leave you feeling out of control and socially vulnerable. So some of the people who have most to gain hedonically from mindfulness training may have the most to lose in terms of their strategy for social control.