How do you live with not knowing?

The short answer: you have never known. You had a story that made it feel as though you did, and the story has gone, and what you are calling uncertainty is just the view with the story removed. You can live here. People do, and many of them say it is the first time they have felt awake.

Not knowing is not a crisis. It is the baseline. Everything else was furniture.

What certainty actually was

A plan with a feeling attached. The plan said: this, then this, then this. The feeling said: and it will be fine. Neither was knowledge. Both were useful, and when one of them failed, through illness or loss or a world that changed under you, the other went with it.

So the thing you miss is not knowing the future. Nobody has ever had that. It is the sensation of having a map, which is different from the territory and was always going to run out at some edge.

Why it feels unbearable

Because the mind treats an open question as an emergency. It will generate futures all day to try to close it: the bad ones, mostly, because the bad ones feel like preparation.

They are not preparation. A worried future is not a plan; it is a rehearsal for a performance that has not been scheduled. You cannot prepare for a specific future by imagining it, because the real one will be a different shape. You can only prepare yourself: your health, your money, your people, your habits. Those travel into any future.

The only question that has an answer

Not "what will happen". That one is closed to you, and it always was.

"What can I do today that would be good in most of the futures I can imagine?" That one is open, and the answer is usually dull and sturdy. Keep the body working. Keep two or three people close. Keep a little money untouched. Keep doing the one thing you are good at. These are the moves that are right whatever comes, and doing them is what living with not knowing looks like from the outside.

What people find

That the fear was of the question, not of any particular answer. Once you stop demanding an answer, the question stops being an emergency and becomes what it always was: a horizon. You walk towards it. It moves. That is not a failure of the walk; that is what horizons are for.

Some people describe the shift as relief: the exhausting job of pretending to know is over, and nothing bad happened when they stopped.

Where this is in the book

Horizon Without Answer is the last scene of chapter two. A man cannot sleep in a city that has given him everything, and something in him has already decided to leave long before the rest of him can say why. The scene is about living inside a decision that has no map on the far side of it, and the book is honest that there isn't one.