When Pluto was downgraded, I had to explain to DS the criteria for planets and why Pluto no longer qualified.
Ds8 was sooooo bummed out about this. He wouldn't even let other people talk about it around him. I think he was 6 or 7.
One frustrating thing is that it sometimes feels like other people assume you are a terrible parent because yours is the overly sensitive child, must be spoiled. (Our dd2, who turns 3 in about 3 weeks is very sensitive too, and we are having conversations about bones, blood cells, all the equipment in the doctors office, etc. )
Welcome TMJ!