After Leon's daily dose of self-harm, that was the training to level up his Fire Resistance, Leon created another hideout hidden in the layer of earth and rocks of the ceiling of... whatever the hell he was. It was already more than clear that he wouldn't escape that hellhole anytime soon, but he decided to create a mithril needle every day to increase his digging speed. Instead of stopping one hour from repairing those, he would use another to open the path once a needle loses its tip. He would fix them later once he stops to rests.
"It is also a good idea to use several needles at the same time to open the path faster, but that also means that I will have to decrease my sleeping hours even more."
It wasn't the same thing, but Leon decided to use the moments he uses Zen as moments of rest... it wasn't a good idea, but he had no other choice. As long as Sleep Resistance keeps leveling up, the effects of his tiredness would decrease, probably.