The thing that you think is hijacking you IS you. The thing that is being hijacked is the creation you have made according to what you have been told you should be. The bit that's missing is the bit that respects and takes care of the real you.
Emotions aren't supposed to be rational, and more than children are. We all have a job to do, with our emotions, as adults. We have to recognise what they're telling us, and soothe them. You don't do that. You try to pretend they're not happening, and then they go nuts because they're desperate be heard, and then you can't keep them under control and you do something that you feel is embarrassing. And then you compound it, by hating the part of you that does embarrassing things.
The problem comes waaaaaay before you do something embarrassing. It comes before you hate any part of yourself. It comes when you have a negative feeling, just a small one, and you say to yourself 'I'm just being silly to feel upset about this.'
You don't need to convince the inner you that the example you gave was just work, and nothing personal. That's a way of invalidating her, and telling her she's making a mistake to feel how she does. That makes her feel worse; it leads to tantrums. If you keep trying to convince her, eventually she'll blow, and she'll scream 'I don't CARE that you think it's not about me!!! I needed some love and HE WASN'T THERE!!!' and you'll say something similar and you'll feel embarrassed. You need to listen to her, and understand her, and nurture her. 'I know you needed some love and he wasn't there. I'll look after you now.'
Your adult side knows that you can't expect another person to take care of you all the time. That's why you think your feelings aren't acceptable. But they are acceptable. The person who needs to take care of that little girl isn't him, or anyone else external: It's you. Stop silencing her. Stop telling her you don't like her. Stop making her feel silly for having her feelings.
When I did this for myself, I collapsed in a corner and my inner little one cried and cried and cried, and I held her (and me) physically, in a strait-jacket-style hug, for AGES. And then I was terrified, because I realised like a punch in the face that I was responsible for me. It's a hell of a task, but after a while, the child settles down. When you listen to her, once she's stopped screaming and crying, you'll hear her voice as your boundaries. She's the one who quietly says 'I don't like this...' when you hear somebody walking behind you at night. She's the one who says 'I feel left out' when your new friend isn't inviting you on group outings. She's the one who says 'I feel like I need more love' when your partner is at work more than you like.