In a healthy intimate relationship, the partners don't have to be turned on by each other all the time, says Dr. Keith, "but they do need to be turned on by each other regularly." Every couple has a balance of how much sex is needed to keep things vibrant, and it's the responsibility of each partner to make it happen. For many couples, this is something that must be learned and practiced. Here's how.

In this two-part series David Deida gives one of the finest summaries of his work ever recorded, offering a provocative and insightful exploration of the intersection between sex and spirituality.