How to Prepare for an Ultramarathon?

When i feel like i've really started to understand just the psyche of running, say, a hundred mile race, is when i found a way to an mentally practise those parts of the race that you can't really physically do en training. The unique thing about ultra marathons is, no unlike a tenca a half marathon, i'm going to go get nowhere near race day distance in training. So you find these ways to put yourself in those moments in training, so that when you get to the race itself, it doesn't feel so foreign or so far background.