Parents beget children in order that these children will be able, as the phrase goes, to “make their fortune” in the world. But as the other phrase which speaks of “the rat-race of pleasure” suggests, this is much harder than it is often assumed to be. Even after some extraordinary improvement in their circumstances or after some amazing stroke of luck people tend to slip back, after some time, to some much lower level of happiness. Things are different when it is a matter of a great catastrophe in people’s lives: in such cases it tends to take a much longer time before people once again acquire their former contentment.
Whoever acts in such a way that another human being begins to exist is responsible for the fact that there now exists one more being who may possess, indeed, in the words of the US Declaration of Independence, “an inalienable right to the pursuit of happiness” but who is constituted, in fact, in such a way that it will always be difficult for him to maintain himself for long on a very high level of happiness, whereas a single stroke of adversity will often leave him permanently discontented.
 See, for example: Baumeister et al., Bad is stronger than good, S. 326.