Elementary age children sometimes have big, difficult feelings that can be hard for them to manage and work through. The demands of growing up, coping with disappointment, feeding off of the stress of adults can all be triggers for epic meltdowns.
A Think, Feel, Need chart is a useful tool for helping young school-aged children express their thoughts and feelings and move to solve problems with greater independence. This is a resource that I got from a beloved preschool counselor with whom I had the pleasure of working in a transitional kindergarten program a few years ago. You can use pre-drawn pictures of a generic little boy or girl; like the one below, or a quick sketch of a stick figure child will do.
First, talk with your child about what they were thinking when the triggering event occurred and write their words near the head of the drawing. Then talk with them about what they were feeling during the triggering event and write their words near the heart of the drawing. Finally, talk through what they might to do or have done for them to improve the situation or make it better, helping them develop a quick plan of execution.