"Happiness," writes Ayn Rand, in an important elaboration of her definition,
is a state of noncontradictory joy—a joy without penalty or guilt, a joy that does not clash with any of your values and does not work for your own destruction, not the joy of escaping from your mind, but of using your mind's fullest power, not the joy of faking reality, but of achieving values that are real, not the joy of a drunkard, but of a producer.
Since joy of this kind involves the achievement of values, it demands values (as against whims); a passion to attain goals one is convinced are right (as against uncertainty about goals that are arbitrary); in a word, purpose (as against drifting). The rational man fulfills this requirement. The irrational man does not. Qua irrationalist, what moves him is not the quest for positives, but the avoidance of negatives. In psychological terms, he exhibits not healthy self-assertion, but neurotic defensiveness. In Ayn Rand's words, he exemplifies not "motivation by love," but "motivation by fear."
"Love" in this context means the desire to gain and enjoy a value; "fear" means the desire to escape a disvalue. The distinction pertains to a man's primary motive in a given undertaking. As examples: the man who struggles to create something new in his work (and who may, as part of the process, have to fight many obstacles placed in his path) vs. the man who wants primarily not to get blamed by the boss or fired—the man who seeks a passionate romance with a kindred spirit vs. the man who sleeps with anyone because what he wants is not to be left alone—the man who tends to his health in order to be free to live and act vs. the hypochondriac obsessed with not being sick—the man who turns to Rachmaninoff for melody and inspiration vs. the man who turns to Schonberg in order not to be passé and not to be too awake—the presidential candidate who has something to say in a TV debate, who wants to make a case to the country and win the argument vs. the candidate who wants only not to make any mistakes onscreen and not to lose.
In one sense, both the above types of men are "purposive"; both are "after something." They are not both "purposive" in the moral sense, however, because morality is a means to survival, and the goal of life, as Ayn Rand points out, cannot be attained by the zero-seeking method:
. . . achieving life is not the equivalent of avoiding death. Joy is not "the absence of pain," intelligence is not "the absence of stupidity," light is not "the absence of darkness," an entity is not "the absence of a nonentity." Building is not done by abstaining from demolition; centuries of sitting and waiting in such abstinence will not raise one single girder for you to abstain from demolishing .... Existence is not a negation of negatives. Evil, not value, is an absence and a negation ....
Happiness is not an absence, either; nor is it some guilty pleasures that serve merely to lessen anxiety. It is not what you feel when you stop beating your head against a wall. It is what you feel when you refuse ever to engage in such beating, when you esteem and protect your head as a matter of principle. Happiness, the reward of life, is an aspect of life. It too requires values, not merely avoidance; and, therefore, a functioning mind.
Just as man cannot achieve self-preservation arbitrarily, but only by the method of reason, so he cannot achieve happiness arbitrarily, but only by the same method. The method is the same because self-preservation and happiness are not separate issues. They are one indivisible fact looked at from two aspects: external action and internal consequence; or biological cause and psychological effect; or existence and consciousness.
Dr. Leonard Peikoff, "Objectivism: The Philosophy of Ayn Rand", p. 338-339.