No matter which one of the relationship stages you're in, your woman will open wide to you sexually only when you learn how to turn her on. What this means, is being able to connect with her at a mental and emotional level. Engage her in a way that values her as a person. Engage her in a way that shows her you understand her wants and needs.
But if you don’t know how to turn her on, she will only go through the motions (at best), no matter how knowledgeable of female anatomy you are, how sophisticated your technique of finding the G spot and how many love making positions you master.