That feeling in your stomach that tells you that, without a doubt, you are about to totally fuck this girl.  That was it.  My younger sister's best friend.  She had her parents place to herself the whole weekend.  And a nice pool in the backyard.  And I got her little text around noon.  When I got there, there was nobody else, just the two of us.  We swam naked together in the sun, laughed, played at being old friends and how I had known her since she was 13.  She was now 19.  

 And then, on her parents bed with the french doors still open to the yard, I pinned her knees up by her ears.  She lay there gripping my ass while I let my hips roll against hers in a slow circular rhythmic process.  Smoothness gave way to deep thrusts, slow rhythm gave way to the fastest pounding-humping thrusts our bodies could manage against each other.

 And we both just came so fucking hard.