Coincidentally the first short story in the latest Interzone ('Everlasting', by Alastair Reynolds) was about the same hypothesis as 'Paying it forward' (short story I didn't like, discussed yesterday). This is the hypothesis that there are huge numbers of branching possible worlds, and that we exist at the end of whichever branch, however unlikely, has produced our existence, and our continued existence to this point. Thus, looking back, we will always see this long line of remarkable coincidences which has allowed life to develop, and our own life to be spared. Reynolds compares this feeling to that of the Queen, who on waking up might be forgiven for thinking to herself 'Bloody Hell, I'm the Queen'.
Bloody hell. I'm alive.
The Reynolds story is much, much, better than Paying it forward, and begins to explore plausible human reactions to our massive good (?) fortune in existing at all. One thought - I have been lucky all my life, just to be alive at all, but according to this hypothesis, there are infinitely many future 'me's, and for most of them, the run of luck has come to an end. But each me which survives will look back, and feel that the luck has continued. By definition. For all the others, the carnage starts now.