When you love someone who loves and marries another

 "As if I would nurse my resentment, Nastenka! As if I would drive a dark cloud across your bright, serene happiness, as if I would inflict misery on your heart with my bitter reproaches, wound it with covert pangs and make it beat anxiously in your moment of bliss, or crush even one of those tender blossoms woven into your dark curls, when you go with him to the altar . . . Oh, never, never! May your sky be clear, may your sweet smile be bright and happiness, which you gave to another, a lonely, grateful heart!
God in heaven! A whole moment of bliss! Is that not sufficient even for a man's entire life? . . ." - Fyodor Dosteovsky, White Nights, Page 56