Joe Simpson’s memoir of survival, Touching the Void, focuses on the battle within:

I had never been so entirely alone, and although this alarmed me it also gave me strength. And excited tingle ran down my spine. I was committed. The game had taken over, and I could no longer choose to walk away from it. It was as if there were two minds with me arguing the toss. The voice was clean and sharp and commanding. It was always right, and I listened to it when it spoke and acted on its decisions. The other mind rambled out a disconnected series of images, and memories and hopes, which I attended to in a daydream state as I set about obeying the orders of the voice. I had to get to the glacier. I would crawl on the glacier, but I didn’t think that far ahead. If my perspectives had sharpened, so too had they narrowed, until I thought only in terms of achieving predetermined aims and no further. Reaching the glacier was my aim. The voice told me exactly how to go about it, and I obeyed while my other mind jumped abstractly from one idea to another.