In a recent book on marriage, Ray Ortlund writes:

The key to understanding the sexual wisdom of [the Bible] is to combine both form and freedom, both structure and liberation. Conservative people love form and restraint and control. Progressive people love freedom and openness and choices. Both see part of the truth, but wisdom sees more. Wisdom teaches us that God gave us our sexuality both to focus our romantic joy and to unleash our romantic joy. When our desires are both focused and unleashed—both form and freedom—our sexual experience becomes wonderfully intensified. A marriage can flourish within both form and freedom, because sex is like a fire. In the fireplace, it keeps us warm. Outside the fireplace, it burns the house down. Here's the message of the Bible: "Keep the fire within the marital fireplace, and stoke that fire as hot as you can."