The number one secret to good sex is to surrender.
You've got to surrender to the act. Let go of the crap in your head and get completely and utterly in your body, in the flow, surrendered to the pleasure of the experience.
Paradoxically, being present in your body enables you to transcend your body. It enables the boundaries of your physical self to dissolve it and allows you to get into transcendent states where you lose touch with the physical plane and get into more spiritual, ecstatic planes.
There's an exercise I do in my workshops - usually very early on because it's so instructive - where I enable people to get present in one side of their body and not the other. They're always amazed at the difference. One side feels warm and alive and tingly, the other feels empty and dead. When I point out that they mostly go through life with their bodies feeling dead like that, they realise what they're missing out on, and hopefully they then pay a lot more attention to what I'm teaching!
We then do more work on breath and becoming centered and heightening sensory perception and lots of other delightful exercises that get people out of their heads and into their bodies. It might not sound all that relevant to sex, but it's fundamental. In fact it's fundamental to living.
It takes dedication and application and practice to live and make love with that level of presence and to be able to surrender so fully to the experience.
Personally, I think it's worth it.