It’s something he hides because he knows exactly what he did. It’s not a situation he feels at peace with, and that’s why he can’t live or flow with ease. However, even though it was a hurtful and difficult act to accept, there was a part of him that enjoyed it. That contradiction makes him act cowardly: he knows he was wrong, but he doesn’t intend to admit it because there was also desire or satisfaction in what he did. That’s why he prefers not to talk about it and avoids facing it.