Katniss loves getting old.
When the first strands of gray begin to appear on her head and decorate her hair with - what to Katniss - looks like silver threads. When the wrinkles form in her eyes on her cheeks and she realizes they are from all the smiles she has given over the last decade.
She begins to truly find herself beautiful, for the first time. Well, she always thought she's average. But today she feels satisfaction every time she looks in the mirror.
There were few she could know who had the privilege of growing old. She is one of those lucky ones. She doesn't feel completely worthy, but she's happy. Especially seeing her love grow old alongside her.
Peeta's blond hair masks the gray, but Katniss can see the slight change from gold to silver.
What really show his age are the freckles. When his skin thins with age, it becomes covered with brown spots on his nose and cheeks. Along with the white beard, he looks just like his father.
Katniss thinks he's so beautiful.
How lucky they are to see themselves weak, wrinkled and old in the mirror. When fate tried to kill them before their time and freeze their childish faces in death.
So every knee pain, every gray hair, every birthday is proof that life can improve.