"This Is the WORST DAY EVER!"
This exclamation was made by a highly sensitive child (HSC), when, after a wonderful day with hours of fun and joy, her dad said "no" to going back downstairs (once she was already in bed with lights out). She insisted she needed to check on a Magnatile structure she had been working on earlier that day.
I can't tell you how many times a week I hear stories like this from parents. Their HSC has a great day with lots of good stuff; and then one, often seemingly minor, event/disappointment happens and everything is ruined.
After decades of working with families of HSCs, and parenting my own, I understand that this is often part of the deal with these deeply feeling kids: they live life at the extremes. They are ecstatic or enraged. They tend to process their experiences in this all or nothing, black and white way. It's all good or all bad. They have a harder time living in the gray.
The temptation, naturally, is to try to get them to see that there was so much good in their day, to talk them out of this all-encompassing, negative state, which seems so unfortunate and sad—for them to see the world this way. But that usually results in the HSC, in reaction to being told how to feel, doubling-down to prove to you that in fact, everything is indeed ruined.
Keep in mind that this doesn't mean the good stuff isn't getting through or having a positive impact on them. This awareness may also help you avoid the temptation to try to get them to acknowledge it or feel it in that moment.
Instead, focus on their feelings, without buying into or trying to refute their assessment.
"I know you're disappointed/angry that I won't let you finish your structure when it feels so important to you right now. But it's time for bed. You can finish it in the morning. I know that feels hard."
In a quiet moment, you can help them gain the self-awareness that is so important, for all human beings but especially for HSCs. "You have really big feelings. When you are happy and having so much fun, like when were splashing in puddles all the way home in the rain, you feel amazing. When you are sad, or mad, or frustrated because you can't have something you want, those feelings are also really big and overwhelming and sometimes eat up all the good feelings. You can't remember those positive feelings in those moments, even though both happy and hard things happen for everyone. That's just being a human." The greater insight and self-acceptance kids have, the better they are able to recognize these patterns and be less reactive to them.