Draw a tall thermometer on paper with the bulb at the bottom. Explain that the bottom is a tiny bit of a feeling and the top is the very biggest.
Name a situation — losing a turn, a scraped knee, a friend saying no — and ask your child to point at how big that feeling would be.
Do a few of your own too, out loud. Comparing sizes matters more than agreeing on them.
Children often experience feelings as a single on-or-off state, which is why small setbacks can produce enormous reactions. A visible scale introduces the idea of degree, and a feeling with a size becomes something that can be described instead of only discharged.