I already love in you your beauty, but I am only beginning to love in you that which is eternal and ever precious – your heart, your soul. Beauty one could get to know and fall in love with in one hour and cease to love it as speedily; but the soul one must learn to know. Believe me, nothing on earth is given without labour, even love, the most beautiful and natural of feelings. <...> But the more difficult the labour and hardship, the higher the reward.
Explanation:
Count Leo Tolstoi to Valeria Arseneva, his fiance. November 2, 1856