Willpower

From early morning until dark, often more than eight hours on his feet, day after day and month after month he directed the work. It was certainly not his work to do this, but he was determined to ensure it was done not only quickly, but economically, and there was no one else with the will power and stamina it required to take his place. It was in ways such as this, with indefatigable determination and unflagging perseverance, that Shoghi Effendi made of the Holy Places at the World Centre what we see before us today.
(Rúhiyyih Khánum, The Priceless Pearl, p. 243)