Let's use the old cooking metaphor here. When you're just starting sex is like going to eat at a fancy restaurant for the first time. It's amazing, but in a kind of surreal way. You have no idea how anything is made or what's in it or even (at the weird restaurants) exactly what it is that you're supposed to put in your mouth.

When you're older you see the craft involved. You start to notice style. You can tell what's a personal touch and what's cliche. You recognize flavors and ingredients. You taste things not as a passive diner but as a fellow chef, and have a good idea of how to get from point A to point B without expecting a miracle to intervene.

Well, I will try to say something which may or may not be useful. I think when you are younger you want to impose a certain form and structure on sensation. It will depend on the particular person of course whether this "imposing" is by means of fantasy [imagining the encounter; imagining how it will be described afterwards; thinking about what to do, what one should do, what "one does"], or by means of action [worrying about how to act so that things don't get out of control; or do get out of control; but in any case somehow trying to have a certain effect].

After awhile you become much more sensitive to the logic inherent in the situation, you allow it to chart its own course. You become alert, responsive, able to listen, also able really to speak; you are no longer the first time dinner guest speaking up to cover pauses in the conversation, nor do you hesitate to make direct remarks, to speak freely, to go deeper. The unknown becomes illuminated, without losing its mystery. You can relate to the other person purely as they are, rather than as some kind of an archetype. Actually what made me want to reply here was reading this thought said much better in the posts discussing a completely different topic, how to do creative work: post.