The younger the child, the more obvious they make their unhappy state. They may become hypersensitive, aware of itchy labels, twisted tights, noises that they wouldn’t otherwise even notice. Little things bother them. Tantrums become deeper, more intractable. Sleep patterns change. You can often see little changes in their posture: shoulders raised, fists clenched. Most of all, they are much more easily “set off” than usual; their emotional switch has a hair-trigger sensitivity.