John Dickson commenting on G.K. Chesterton’s thoughts on pride and humility. “human pride is in fact the engine of mediocrity. It fools us into believing that we have ‘arrived,’ that we are complete, that there is little else to learn. Humility, by contrast, he said, reminds us that we are small and incomplete and so urges us on toward the heights of artistic, scientific and societal endeavour:” John Dickson, Humilitas: A Lost Key to Life, Love, and Leadership
BTW NOTE: I think it should be said that pride can make someone mediocre, but it might not. It can also make someone a perfectionist that is always pressing on in search of something better. But this too can become a vice. Humility finds the sweet spot.
A Pilgrim's Theology 