Realizing that your mind is the sexiest part of your body. I had a gf that could get me so worked up just laying next to me and whispering what she was about to do with me. Sometimes she would whisper a fantasy of hers in my ear. Ummm WOW! I even got pretty good at it too.
Change it up and Spice it up. I agree with Diane above.
Knowing your own body and what feels good to you and what you like. How is your lover supposed to know you if you don't know yourself? This ties in I think with wanting to know yourself and wanting a "Great" sex life.