I've still got the mug.
I've tried buying stuff (like books) that I had when I was a kid, but it's not the same. I'm not really into receiving gifts either...
Sorry for the looooooooong raaaaaaaamble but I guess it's about the feelings that stuff represents. Thanks for starting this thread and letting me get some "stuff" of my chest,
2cents
I'm glad you kept the mug. And I am really sorry about all your possessions from years ago. I agree with you that you cannot recreate or retrieve these things, but perhaps you could write more about them. See how many of the books you can remember, and what was in them, and describe them in detail. Just to show that in a way they are still with you.
My brother is obsessive about throwing away anything that is either connected to the past or else broken. He 'encouraged' me to throw away all my childhood diaries one time, and I let him do it. I have always regretted that. Another part of me sent to the tip.

I used to keep photographs in them, and mementos of one kind or another, and wrote a page every day for years and years, including at the time my nana died. All the memories were there. One of the photographs was of our great grandmother, and I have not seen another copy since, so it has gone, I am afraid. Stupid really. And he made our parents throw away his old carry cot from when he was a baby. I regret that loss too. It couldn't have been used now, because it would not be safe enough, I suppose, but it could have been kept. I did it to make my brother happy. He wanted me to prove that the past was gone and didn't matter.
I think this is a reaction against my Nmum, who is a hoarder, and keeps everything, which seems to be how she tries to find love or satisfaction or fulfillment somehow. It gives her a thrill for a short time to buy something, especially if she gets it cheap and can believe she has robbed or cheated or got a bargain somehow from someone else. There is a strong element of oneupmanship in her acquisitions. So my brother wanted to be different, and so threw stuff away.
Now he has a home of his own, however, it is strange to see he has started some collections of his own. Vintage toys and train sets. Weird.