St. Maximos the Confessor: The relationship between prayer and love for God

 He who genuinely loves God prays entirely without distraction, and he who prays entirely without distraction loves God genuinely. But he whose mind is fixed on any worldly thing does not pray without distraction, and consequently he does not love God.
+St. Maximos the Confessor, from The Four Centuries on Charity, century 2, #1.