The early Christians saw the end of the world as the moment when God would rescue them from the current persecution they suffered. It was a pastoral call to remain faithful during hardship and to have hope of rescue in response to real immediate danger. I think the main difference was the surrounding circumstances at the time. Indeed, a warning about the imminent end of the world can provoke repentance and charity while shaping a communal identity. Their beliefs about the apocalypse were not new but inherited from their jewish tradition and knowledge of the world.
During a crisis, when it's impossible to see a way out, I can see why it seemed like the end of the world, and why they thought an apocalypse was necessary to save the faith as the Christians were on the brink of extermination.
However, I think things are different today. Different circumstances. And symbolically, the world is ending for each of us individually, so the words are still true in some sense. I think the response should be the same: repent and love Jesus, live well, live morally with charity. But enlightened by the passage of history and its stubborn unwillingness to abruptly end, I see no reason to fear an apocalypse as our culture has ingrained us to. The early Christians saw the end of the world as God bringing relief from a hopeless situation, but today we see it as an unmitigated disaster beyond compare that destroys everything. I don't think it's healthy to dwell on the latter.
Focus on eternal life is literally the longest time-preference possible and in this anno domini should be ever present because we don’t know the day or hour when this age will end for us personally or for all men universally.
“No, I say to you: but unless you shall do penance, you shall all likewise perish.
Or those eighteen upon whom the tower fell in Siloe, and slew them: think you, that they also were debtors above all the men that dwelt in Jerusalem?
No, I say to you; but except you do penance, you shall all likewise perish.”
