When she usually tried to kiss me goodbye I would shrimp out of her hug and make disgusted faces, like I was a kid squirming away from an affectionate relative.
I got to a point last fall though where I lost the will to resist. We were at a mutual friend's apartment, and she was getting up to leave. She turned back to me, sitting on the couch, and bent over to try and kiss me. I didn't move and she hit my lips, straightened up immediately and looked confused.
"You let me kiss you! You never let me kiss you!"
I told her I had no idea, she laughed and left. The decision to let her kiss me wasn't made by me. I felt like I had been out of the room while it happened, the equivalent of someone brushing your arm while passing on the street.
Nothing has ever come easier to me, since then.