Nice ad for "sword" sportfood products, though.
For one thing, running 100 mile races isn't a very good standard for willpower or self control.
There is virtually zero use for this capability, so whether you spend 5-10 hours a week to do so or not isn't really a question of self control.
It's a question of what activities/hobbies you want to pursue in your free time.
Staying fit is a good-for-you type of thing, but you don't have to do anything close to that level of training to stay fit.
My advice, whether you want to get/stay fit or achieve some athletic endurance goal is to make sure you find a way to enjoy the training.
It takes consistent long-term training and you wont't have to worry about your willpower Or self control if you enjoy doing it.
Along those lines: start slow - the hardest and most painful part is getting started. E.g., use a C25K program; find your own goals - whether that's completing 100 mile runs, or a 5K PR, or 1000 miles this year, or an 8:00 pace or a 365 day running streak or whatever.