Song.

Every song has a memory attached to it. What do you do when you don't want to remember something anymore? What do you do when the song painfully reminds you for one particular incident? You remember where you were sitting in the room. You remember what he was wearing. You remember the book that lay half read next to his pillow. You remember what he said. You remember how you felt. You remember feeling those things whenever you listen to that song. Painful. You feel them again.

What do you do?

You either stop listening to that entirely or you move on. You listen to the song and form new memories. New feelings. And then one day, you are in your room, you have your player switched on in Shuffle mode. The song begins. Slight fear. The song continues. And then, you don't feel That anymore. You remember it, but it doesn't hurt. You smile and let the song end and it doesn't hurt anymore.

P.S. My friend Manoj calls it a mental block. Being unable to listen to a song because it brings back bad/sad memories.