Thoughtful Thursdays - sentiment

Why do people attach memories to objects? What gives something sentimental value? Usually it's for something/someone that has been lost. Soo when your grandmother passes away you might attach sentimental value to the blanket she knit for you. Or a souvenir would be an example too, of a trip or experience that is over. Anyhoo, why does that happen? On a mostly related note, a human is the only species that feels a sense of loss if I hold up a pencil, tell you his name is Steve, then snap it in half. Though that's more empathy than sentiment... Still attaching greater value to an otherwise less valuable object. Going back to the blanket example, lets say the average person would be willing to pay $40 for such a blanket. I might be willing to pay upwards of $100 because of the sentimental value it holds. But I still haven't really said anything about why that happens. I know that the brain associates certain memories and sensations with each other if they happen often together. Example: mom's house always smells like cookies. I smell cookies, I think of mom. I don't know the rest of the brain chemistry, but I know that I don't attach emotional value to physical objects very often at all. Thoughts? Could you follow this post?