The Deeper Symbolism of Freemasonry from The Meaning of Masonry by Walter Leslie Wilmshurst.

“Now the man who so develops himself, speedily becomes more conscious of the difficulties of his task, more sensitive to the obstacles the life of the outer world places in the way of the spiritual life. But he is taught to persist with fortitude and with prudence, to develop the highest within him with ‘fervency and zeal.'” [via]