I realized yesterday how cumulative emotions are. Bug (5) got really upset by something I'd said, and was expressing his upset by crying and yelling and stomping. I sat with him for probably 20 minutes while he worked it all out. That might seem like a long time to be upset about something most people would find trivial, but it's what he needed. And now that he's expressed it fully, he doesn't carry it around with him to add to the next time he feels those feelings.
In working through my own past repressed feelings, I can say it's really hard. And it takes so much time. So much time, because it all adds up. Like rollover minutes, lol. So when you're in the throws of your child's emotions, maybe keep that in mind. You're doing yourself and them a huge favor by holding space for them to safely express themselves. All feelings are valid.