What a great thread with a great amount of wize input.
I'd like to add a few more items. Use your child's intelligence to advantage. I'll agree that the same method isn't going to be appropriate in every scenario, however, keeping track of concerns and making a list over a period of a few weeks / months, then sitting down to say, "Here are the concerns that you've had as of late, lets go over them and see which of your concerns actually became issues in reality." Most GT kids are pretty good seeing patterns. They may very well realize that their concerns are ill founded a great percentage of the time and they've invested a great amount of negative emotion for no good cause.
If you're a family of Christian belief, take some time to review what scripture has to say about worry. That went a long way with our eldest DS.
