Plot twist: Voldemort started using Occlumency to block his connection to Harry in book 6 because he got tired of constantly hearing Harry's thoughts about Draco's sparkling light grey eyes and sleek blond hair.
Voldemort, in the middle of a meeting, grabbing his head in agony: No, no, not again
Lucius: Whats the matter my Lord?
Voldemort crying: I can't go through the teenage angst again. Tell your son to stop.
Lucius: What did Draco do-
Voldemort: JUST TELL HIM TO STOP.