[The answer is he had been compromised a lot, which is only further proven when the mere mention of his family has him wincing. As they do so often, his thoughts return to that bridge on Starkiller Base, that moment when he could have activated the lightsaber - or let go.

Every night when he lays in bed in the darkness and quiet, he wonders what if he had let go.]

Compassion is a sickness. My Master has taught me that it must be killed. I eradicated the last of it within me when I killed Han Solo. [But the scavenger still lives, and keeps feeding this weakness. It's enough to send a better man than him into a rage.]

My family will die, as will you. There will be no mercy next time. I will show you how much compassion I have left.