why he was up all night praying. Because it was the only time he could find to be alone in the quiet! He was so busy that he literally didn’t have a moment alone all day long, so all he could think to do was send his apprentices away and stay up all night on a mountain (the word eremos isn’t used here, but a mountaintop at midnight fits the bill). Because he knew that time alone with his Father was even more important than sleep itself.
