Isn't sexual -- or emotional -- intimacy enough? "No," says Christian psychologist Dr. David Clarke. "Spiritual bonding is the process by which a couple cultivates the presence of God in their relationship," he says, "and it's the only 'glue' that sustains relationships long-term." Working with hundreds of couples, Clarke observes that when we take specific steps to keep God at the center of our relationships, every area of intimacy is energized...