Happiness is nature's way of regulating our behavior. If a person with gene A is happy doing activity X, and a person with gene B is happy doing activity Y, and activity X leads to having more children and activity Y leads to having less children, then gene A will occur with increasing frequency in future generations and gene B will occur with decreasing frequency.
When we think about activities which make us happy, we see that all of these activities are related to survival and procreation. People like to eat, and this was probably important because securing an adequate supply of food contributed to a longer life when we were caveman. Of course people are happy when they are having sex, which is an activity crucial to passing on one's genes. People claim that their children make them happy, and this is also crucial to passing on genes because children require parental attention in order to survive to adulthood. People get happiness from their social activities and friendships, and having friends could mean the difference between life or death back in the caveman days.
We also are happy from having a higher status in society. For further evidence, read my post about the Pew study of happiness. This is probably especially true for men, because due to more boys being born than girls (about 105 boy babies for every 100 girl babies) and polygamy, there aren't enough women to go around in order for every man to have children, so the lowest status men see their genes die off just as surely as if they died from starvation. It is for this reason that the quest for status is one of our most basic human drives, and why people who have higher status (as measured in the Pew study by income) are happier.
Utopian communists understood that low status causes unhappiness, and they endeavored to fix the problem by designing a society where everyone is equal. Unfortunately, it is impossible to create such a society, because the desire for status can no more easily be quenched than the desire for sex. Because people differ naturally in ability, in any society where there is even the slightest bit of individual freedom, people will manage to sort themselves into high status and low status, and because the distribution of status is a power law distribution, those with the highest status will always dwarf those with the least.
Utopian libertarians, like the authors of Cafe Hayek, also need to understand this issue. If we design a society that doesn't address the unhappiness of those at the very bottom, it will be sure to fail even more readily than communism did in the Soviet Union.