[I]t is difficult to escape the conclusion that all lives contain more bad than good, and that they are deprived of more good than they contain. However, such is the affirmation of life that most people cannot recognise this.
One important explanation for this is that in deliberating about whether their lives were worth starting, many people actually (but typically unwittingly) consider a different question, namely whether their lives are worth continuing. Because they imagine themselves not existing, their reflection on non-existence is with reference to a self that already exists. It is then quite easy to slip into thinking about the loss of that self, which is what death is. Given the life drive, it is not surprising that people come to the conclusion that existence is preferable.
Asking whether it would be better never to have existed is not the same as asking whether it would be better to die. There is no interest in coming into existence. But there is an interest, once one exists, in not ceasing to exist. There are tragic cases in which the interest in continuing to exist is overridden, often to end unbearable suffering. However, if we are to say that somebody’s life is not worth continuing, the bad things in life do need to be sufficiently bad to override the interest in not dying. By contrast, because there is no interest in coming into existence, there is no interest that the bad things need to override in order for us to say that it would be better not to create the life. So the quality of a life must be worse in order for the life to be not worth continuing than it need be in order for it to be not worth starting. (This sort of phenomenon is not unusual: a performance at the theatre, for example, might not be bad enough to leave, but if you knew in advance that it would be as bad as it is, you would not have come in the first place.)