Step one to survival is being prepared for the worst before having to actually survive the worst. Some might say one of the worst consequences of sex is pregnancy. Fortunately, birth control exists to prevent pregnancy– If you’re prepared.
All of the many forms of birth control seek to accomplish the same goal: prevent pregnancy before it happens.
Some methods are for use before sex. Some for use after; and a few for use during sex.
I generally think about the apocalypse happening in one sudden apocalyptic event that takes everyone by surprise. But what if it doesn’t happen that way? What if the apocalypse is a slow, years-long decline? After all, in some ways, the fall of the Roman Empire could be considered an apocalyptic event. And the empire’s decline took a long time, since it technically didn’t fall until Constantinople fell in 1453 (though, okay, the Western Roman Empire was in serious decline and almost completely taken over by Germanic tribes by the end of the 5th century).