I regularly go for months with very little human contact, partly because of my work. That can be pretty hard if you still want the usual human things, and most people in my situation do, at least in the beginning. That can cause behavioral changes that are not good for you and not good for social interaction when you do come across people. If you aren't prepared for isolation and you suddenly find yourself alone in an End of the World situation, you probably will do rather poorly.

Years of meditation, though, has enabled me to be able to handle isolation far better. It has also taught me to see the world and oneself in a completely different way. Yes, there is meaning beyond living as part of a social group. Now I can sort of see how Indian yogis are able to spend decades isolated in a cave somewhere.

If this is a concern, I would recommend studying this before you actually face prolonged isolation. You develop skills faster if you have teachers and classmates, and these may be in short supply at the End of the World.