The Circle of Control concept is helpful especially for children during stressful situations as it helps children  identify situations they CAN control versus situations they CANNOT control. It's also a great tool to use with children who excessively worry in everyday situations. This is an exercise I do with students frequently. 

If you have a child whose worries are growing, sit down with them and do this activity. Draw a circle on a piece of paper and have them draw pictures, or write things in the circle that they can control about a particular worrisome situation, and then draw or write things outside of the circle that that they can't control. Helping children to see what they have control over (their thoughts, feelings, and behaviors) empowers them, and helps them learn not to waste their emotional energy on things they can't control.