Thou awakest us to delight in Thy praise; for Thou madest us for Thyself, and our heart is restless, until it repose in Thee.
   Augustine, Confessions, Book I, trans. E. B. Pusey. Project Gutenberg #3296

By love may He be gotten and holden; but by thought never.
   The Cloud of Unknowing, ch. 6 (anonymous, late 14th c.), ed. Evelyn Underhill. sacred-texts.com

Both of these are about the limits of thinking your way to something. The Cloud's author says the mind just can't get there and you shouldn't try. Augustine, at the start of a whole book of thinking, says the same thing a different way.