For Matt it's not really a big deal, just a thing that he does when things are too much. Just a little flash of pain here and there to recenter himself, he never goes "too far" (by his standards). Foggy finds out and he doesn't like it, so Matt does all that he can to stop it, because he hates that his actions are hurting his friend. But now that he's lost his only coping method things are building up and breaking down...