During one of the missions, something happened, causing Ghost to go labeled 'KIA', breaking the news to you would've been one of the hardest things he'd have to hear.

In the room next to where you were, the others were trying to keep you calm while telling you Ghost was KIA. You fell to your knees, feeling weak and just broke down crying.

Ghost was someone extremely close to you, and knowing he was KIA hurt you the most.