Following the same thread as my other posts this week (Be A Lighthouse and Understanding Our Own Emotions), I humbly offer this next step. I'm breaking it down step by step because emotional changes are complicated and things seem to come up incrementally.
Emotions are just feelings happening, there's no need to confuse them with actions, events, and choices in the past or future. Even when your emotional child is ranting about something ('I hate you guys, you never get me anything! Everybody else in the world has a phone. I know you hate me or you would let me get one!" for example), what they are really sharing is a window into how they are feeling. Don't get engaged with the thoughts spinning our from their emotional experience, stay with their emotions. See if you can 'hear' their feelings.
That's a kind of radical suggestion. Don't get caught up in what they're saying (obviously, listen deeply and pay attention, and if there are concerning things consider how to handle them, but don't interrupt the emotional sharing to investigate them). Listen to the feelings, even when they are not talking about them directly. Listen to the feelings, even when they make you uncomfortable. Listen without redirecting, problem-solving, explaining, teaching, or convincing.
If your child says something like, "Nobody ever sits with me at lunch because everyone thinks I'm stupid and even when I sit with people they just walk away and I hate my whole life . . " imagine listening without any judgment or agenda. Maybe you would just nod. Maybe you would say something little, "Oh wow," without breaking their flow. Maybe they're open to more, so you say, "Honey, that sounds really hard. I hear how sad you feel." They may correct, saying "I'm not sad, I'm angry. I hate them all." Just follow them.
Here's the important thing--stay away from logic! An emotional person does not need logic, they need presence. Forget what you've learned about emotional support and try gentle and affirmative listening without fixing. See how it goes. Be patient, it can take longer than you might think, especially with a child who isn't used to it. They may have a lot of feelings to express.
Let me know how it goes!
As a mom (to 2 teenage sons), wife, and person in the world, I have been on a long imperfect journey. I have made many mistakes, but with mindfulness, emotional reflection, and lots of support I have learned enormously from those mistakes.