Where do they keep the antibiotics in drug stores? Also how do I get fresh water for the rest of my life. This is the sort of stuff a person would be working on. This assuming that Zombies or crazed bikers gangs don't also survive close by, and show up to ruin your day.
However before this happens you'll need to map out the water tables in your area. Wherever you finally settle down know the location of freshwater streams, and such.
One must learn to think long term,...very long term.
Your life depends on it. This is why so-called primitive folks tend to do this. End of the quarter thinking in this environment will be very fatal. So very long term planning if one wants to go on.
However,...
A safe place to live.
Did the wildlife come through the event. If so you'll need to learn to hunt some. Eventually protection from them. Canned or dried food is only good for at most five years. You'll have to be a farmer/hunter. If you're an urbanite you'll have to learn these skills. This can be done with experience, and reading. Life in the city will be too dangerous in a year or less.
Find a cabin.
I think a very young person of the 21st century may not make it past two or three years. They wouldn't even know what questions to ask. They'll die of infection or food poisoning.
Perhaps even a predator attack.
Btw the commercial seeds will start to go bad certainly within six to ten years. This is why a medium plot farm will be your savior. You'll need to harvest not just the crops, but their seeds, and have a surplus of a year perhaps two of dried veggies or fruit.
This will be hard work. Seriously hard work, but can be done. You'll do it because you'll know your life depends on it.
Again take care where you decide to settle. You'll learn that a flood plain is called that for a reason. Be near a stream not a river. Those flood. Fish will be a major calorie source.
Do art. Paint draw write sing dance this will keep you both sane, and physically healthy. Me I would do one man portrayals of the classics, as well as commercials,...this especially from the 1950's. This would amuse, and center one's sanity.
Remember you are alone in this world. Except for your cats, and hunting dogs.
Maybe going to towns for new tools or perhaps items to amuse. She or he may have a classic Land Rover they keep tuned up for this. A Rover is what I'd have. A good four wheel drive all terrain ride. This could last for some years. After the gasoline no longer clicks.
A Rover can use other mixtures...so I've read.
Although one would have to know where you were, and how to get back to your homestead if you broke down. Remember there is 'no one else'. Only 'you' can save you. How long one lives will be the same as with our ancestors...dumb luck, and your hard work. If the survivor was say 26 at the time of the Event they again with "luck' could live into their 50's certainly,...that is if they wanted to.
A possible reason to go on would be company.
12 years into your farming hunting performing artistic life perhaps a change.
A hunter gatherer group might pass through the area. This unlike the marauders in the films, and books,
would be a pleasant encounter. It took all those years to stumble on your homestead because they may have started thousands of miles away.
You'll trade laugh fuck, and they'll move on.
Though now they know you're there, and they come back a few times a year as their journeys take them through the region.
Same thing.Laugh perform some plays for them trade fuck, and they move on. One day if your a guy some of these bands come back with your daughters, and sons to visit.
If this were me I can see myself taking my extended distant families around the farm in my aged Land Rover.
The little ones amazed having never seen a car actually running.
So humanity at least in the first post Event generations live in peace.
In the future villages towns one day city states.