I found this wonderful activity through Fishful Thinking which is making a positive difference with my children and myself. It is called the Shake Off the Frustration Dance. What a better way to destress and put things back in perspective - by being crazy for a few moments with your children.
I am currently using this activity with my five year old son who is a perfectionist. Many times he has difficulty focusing on and staying postive when a new activity doesn't come to him right away. He gets frustrated and can't move beyond it. So when something gets to the breaking point with him, I tell him it is time to shake all the bad thoughts out of his body. I have him stand up and we start wiggling and waggling all the bad thoughts out. We look so silly and quickly start laughing. After the laughter dies down he is able to re-focus on the task at hand and give it another try.
If the "shake off the frustration" dance doesn't appeal to your child, work with your child to find a ritual that helps him or her calm and refocus. Taking deep breaths, repeating a positive phrase such as "It's okay. I can calm down and get back to work. My frustration doesn't have to stop me." For younger kids, doing something physical to help release the pent up energy that sometimes comes with frustration is often helpful.
Keep in mind, that these techniques will require practice, so don't expect them to work the first time. The more you practice them, the more effective they will be.