Barefoot running on the steppe

From Herdsman to Statesman:

"In the warm summer, it was difficult to herd [the] sheep in the stony desert pastures of the steppe because many of the flocks went to distant areas, and I had to run after them, barefoot... Running barefoot long distances over the black earth at first cracked the bottom of my feet and made them sore, but in due course they became hardened and tough. 'Learn toughness, not rights' I had heard my mother say from time to time..."