Everyone thought it was because I had let him down. Because I couldn't save him. Just like I couldn't save Severus, Colin, Moody, Remus, and Tonks. I should have been there, I should have saved him. It was more than mourning the death of my brother in arms, more than the death of my friend. It was deeper than anything imaginable.
It was seeing him on the train, him checking in on me.
It was him holding me in the dark while I cried.
It was him rescuing me from Them.
It was him being there when I awoke from being unconscious after rescuing Ginny.
It was us whispering secrets underneath the moon.
It was me teaching him about engineering in Mr Weasley's shed.
It was me funding his dream, Weasley Wizarding Wheezes.
It was us kissing in the ROR, long after everyone else from the DA had left.
It was him giving me a promise ring that I would wear around my neck in battle.
It was him proposing to me in the dark while everyone else slept.
It was him tapping me Morse-code at 1 am on the radio.
It was me wearing black, not as family, not as a friend, but as a lover.
It was me speaking at his funeral, placing those unspeakable memories in the pensive.
It was moving on but never forgetting.
It was Mischief-Managed.
It was our story's end.