Having marathon mindset

There was an article about a woman runner who won two of the most difficult 100-mile races and set a record in one of the races of 26:14.08 hours.

The accomplishment of winning two 100mile races is amazing.

Having run marathon distances of 26.2 miles and contemplated entering a 50K race at one time, my thought was what kind of mindset does a runner need to a run that far?