It was the essence of time left behind after pain and suffering.
And this kind of growth was irreversible.
It was like how Snakel's death aged Gu Mengmeng by a thousand years overnight. Elvis and Lea took two years to gradually pull her out of that abyss.
How much love and affection had they poured into her to rebuild her former innocent manner. But only Gu Mengmeng herself knew that there were some things which were irreversible. She had to continuously remind herself to be happy, to be cheerful. She could not let her own emotions drag down the people around her. But this pressure was slowly tearing her apart. One side of her struggling to maintain a smile during the day. The other side of her secretly crying at night.