I found that buying school supplies worked wonders with DS9 this year! He was all worked up about starting school, and then he got to pick out a new backpack and was so pleased with his choice that he actually said, "I can't wait for school to start this year!" Then he clapped his hand over his mouth, LOL!
On a later trip, he got to pick out a locker mirror/caddy thing and got all excited again.
When he starts thinking bad thoughts again, I find some reason to have him check his backpack full of stuff and he forgets his worries in all the excitement of notebooks and pencils.
