Emotional regulation is a skill that takes time to develop. Be patient with your child (and yourself). If you were never exposed to such parenting strategies as a child or young adult, and these skills are hard for you to use, ask for help. School psychologists and counselors can provide information and support as you learn and practice new parenting skills. The goal isn't to eliminate negative emotions, but to teach your child how to handle them in a positive way.
By elementary school, most children can manage “big” emotions. But their emotional development will continue well into young adulthood. Don't expect your child to be perfectly under control. Be ready to offer significant emotional support during stressful situations, no matter their age.
Giving your child tools to manage their feelings will help them for the rest of their life.