How I see negative emotion is, it's similar to what physical pain teaches us.

You touch a burning stove. It hurts. You learn this action -> undesirable outcome and avoid doing it. (Sometimes it can take a few times though!)

Just that with negative emotions, sometimes it's less obvious the cause or it's an interplay between a few. And sometimes, there's a time delay between an action and the negative emotion. That's why self-awareness and introspection helps a lot in learning from your experiences.

I think the "you can choose to be happy all the time" movement maligns negative emotions too much - it can be an important warning "hey something is wrong" system in life. Also, I believe the use of the word 'happiness' often leads to misunderstandings.

You cannot be happy, the emotion, all the time. Hour to hour, day to day, we all go through different emotions.

You can however be more consistently happy, as a perspective on life and approach to life.

That I believe is what people really mean when they talk about 'being more happy'.

But a lot of people misunderstand that, thinking if you aren't feeling weeeee most of the day, you aren't really 'happy'.