Love Lesson

"Love never dies a Natural Death. It dies because we don't know how to replenish it's source."
~ Anais Nin

How can a single person find someone who we know that, no matter how short or long their relationship is, they will always find a way to replenish it's source? How do two people know that their love will never die?
Is the source of their love for each other found in each other or is there a third party source?
A third party source seems to me to be the only way that a marriage would not implode on its self. Without it, it seems that the two lovers would be putting too much pressure on each other.
Love is too powerful and unpredictable for any human to control on his or her own. There needs to be God, a third party, who knows love, inside and out, for two lovers to be able to enjoy the wonderful pleasures of love and minimize the unbearable pressures of it.