How do people fall out of love?

When a couple are young and in love, they care for each other so much that they think, always, of pleasing the other. They compromise, they go to extra effort to make life wonderful for their spouse, they do those special little things...their words are sweet and kind. As the years pass, life becomes harder, the time they have for one another is less, and the beauty of youth is gone. There is very little physical charm left, as there was in youth, and neglect begins. Soon there is no more extra effort, no little surprises, no special gifts, no kind words...unkind words are substituted. Anger grows. And the couple see their life is ending in unhappiness. That is how people fall out of love.