NOTE: SET POST-SERIES. SLIGHT SPOILERS.
Scars, Like Badges
They both have scars. There are the physical ones that go skin deep and that they were like badges, and then there are the mental ones.
Most of the time, the physical scars are easy to forget. Fingers trace them from time to time, remembering, but the pain from them is nothing compared to that of the mental scarring.
War wounds are easy to forget, but the memory of war itself is worse. It cuts with sharp, jagged (and yet somehow straight and smooth-edged) malice. Fierce. Unrelenting. It embeds itself deep, beyond the physical.
The memories seek to destroy what the physical act of war could not. The soul is perhaps what most makes a person 'human'. To be human is to care, to think, to feel, to exist.
War stories, memories, hack at those qualities. There is the constant threat of the softer traits a human should have being irrevocably damaged.
No one should have to deal with war – not at their age. But they have. Side by side. They, Ron, Ginny, and many others fought the forces of evil. Some died. Most were injured in some way or other. All were scarred.
The aftermath was – still is – difficult. Even with their scars though, both physical and mental, they have come out on top. They won the battle, and now all that is left to do is rebuild together and heal.