There is a cosmological theory called the “many-worlds interpretation“. It postulates that everything that can happen, does happen. Every time alternate futures are possible, all possible futures happen and another universe exists following each possibility. So everything that can happen, no matter how unlikley, does happen in one of those universes.
The quantum-mechanical “Schrödinger’s cat” paradox can be resolved by the many-worlds interpretation. In this interpretation, every event is a branch point. The cat is both alive and dead—regardless of whether the box is opened—but the “alive” and “dead” cats are in different branches of the universe that are equally real but cannot interact with each other. (Christian Schirm [CC0], from Wikimedia Commons)
Comics, anime and science fiction have been playing with the idea for quite a while but it is a serious scientific proposition. Most importantly it resolves the Schrödinger’s cat thought experiment.
You can imagine a dizzying number of “Daughter Universes“ splitting off at a fantastic rate. The number of possible universes may not neccessarily be infinite but would still be fantastically large.
Each new “daughter universe” is exactly identical except for that one change. As changes build up, some universes would become incomprehensible able to us. Others would remain so close to ours as to be impossible to detect the difference. Remember the old TV series Sliders? Something is keeping the crew from landing in an unfriendly universe as life could not exist in most possible universes. (However, at the very close of one episode they did land in one where people didn’t wear clothing. :D)
Sliders, Season 2 episode 3, “Gillian of the Spirits”, Fox Television
OTOH, if spacetime is infinite and unbounded, that gives an infinite possible number of universes. We assume that spacetime was created by the Big Bang and therefore cannot expand faster than the speed of causality. (Causality travels at the speed of light in a vacuum. It is the real meaning behind the constant “c” in E=mc2.) We cannot prove this to be true. We may be expanding into spacetime rather than it being created. There may be a patchwork of every possible universe already existing across spacetime instead of new ones spinning off.
Rather like a pachinko game, while there may be a near infinite number of paths a universe might follow, everything eventually narrows down to an exit. It looks like our multiverse may ultimately head back into the signularity from which it sprang. If it doesn’t it will eventually cease to contain life due to “heat death” or perhaps due to the “Big Rip“. Either way, life in this multiverse is done for in a few trillion years. Anything beyond that point is irrelevent.
So when life gets you down, take solace in the hope that somewhere in the vast multiverse there is a version of you that had perfect luck in life and somewhere else there is a version that had the most horrific luck imaginable. Someone who made the right decision when you screwed up and someone else who failed miserably when you came shining through. And a whole bunch of universes where you do not even exist.