My 11 year old neice shows the tendency, too. Had this convo with her not long ago:
"This shirt is too small. Let's put it in the "donate" pile.
But it's my favorite shirt.
I know. But you can't wear it; it is too small for you.
But can't I keep it?
What for?
Because it is my favorite!
But now it's time to get you another shirt that will become your favorite. Time to let this one go to another little girl so it can become her favorite. She will love it just as much as you do. A favorite shirt should be worn, not stuck in a box somewhere.
(Reluctantly) Okay.
Now how about all these Duplo blocks?
No! I like to play with them.
How long has it been since you played with Duplo blocks? You are 11 years old. I haven't seen you touch them for at least 3 years.
But I might want to play with them sometime.
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You get the picture! But I have to admit, I have the problem of doing the same thing with books. I have to force myself to get rid of some from time to time.