I want to describe the behaviour like when I pay attention to a thing, I care about it, I don't want to lose it, I'll carry it wherever I go, and I'll angry if someone throw that thing away.
I found this word when I was looking for the synonyms of sentimental. The antonym itself is unsentimental, so I think I've chosen this word correctly. According to Merriam-Webster, chocolate-box means:
superficially pretty or sentimental.
Can I use that word like in this conversation?:
A: I broke your pencil, let me throw the pencil away. I'll buy a new one for you.
B: No way! Put it back! It was a gift from my late father.
A: Oh sorry. But it's broken.
B: I know. I'm just chocolate-box.
But that sounds super awkward!