It's never satisfying.
As you proceed, your instincts tell you to thrust, but the act becomes tedious, and you start to think again. You ponder what you're doing, and then you realize that it's meaningless, that the girl and you and everything around you will be decomposing molecules chewed-on by worms in a hundred years, and that a fifty years after that, whatever offspring you produce from the act will be decomposing molecules chewed-on by worms. And then you start to get that existential disgust for for the stupidity and the banality of it all, the sheer ferocity with which this dull and repetitive act is parroted across the human community as if it were the most wonderful thing ever experienced in the universe, instead of the mechanism by which our destructive species continues its pointless destructiveness.
And that's when I climb off the bewildered and drunken woman, put on my clothes. and drive home with that sinking feeling in my stomach that participating in such an act again would be a humiliation beyond the capability of words to describe.