My favorite quote from B.K.S. Iyengar. (For the Yogis among you, I practice Pattabhi Jois‘ style, but that’s neither here nor there.)
Intellectuals tend to be arrogant. Intelligence, like money, is a good servant but a bad master. When practicing pranayama, the yogi [makes] himself humble and without pride in his intellectual attainments.”
Page 85 in this book.