Ultracycling

https://jamesmarkhayden.eu/knowledge/men­tal-fortitude

This is good and I've found similar things, in the races and elsewhere.

Some say it helps to break the route into segments and just focus on reaching the next one and I agree to some extent, but for me the better mindset is usually to settle into the thought that this is what I'm doing now and kind of embrace the experience and the present, while not really thinking about a goal, or that the goal is to do what I need and want to do right there to keep moving as fast as I can. I find I enjoy it more like this and am probably faster and better organized. But this requires you to actually want to do it and be confident.

I think there was something about how you learn to handle stressful situations at the when you get used to them, for example during deliberate cold exposure, that they mentioned in the Huberman lab podcast. How it's kind of neurological training for dealing with adrenalin. I went to a cold exposure course too where they said something about this.

Kurt Refsnider has his concept of "normalizing difficult", that you do things that are hard enough during training that it feels normal in a race. At least it means that different kinds of terrain and weather won't feel so surprising if you've dealt with them before. Which indeed is just being confident.