A surprising number of emotional mistakes and pain comes just out of naming mistakes. Someone says he is angry when he is really ashamed. Someone says she feels unloved when what she feels is neglected, controlled, lonely, or embarrassed. Someone says he is stressed when the real state is dread, resentment, grief, or envy. Those are not tiny wording differences, but rather how we feel, accurately expressed They point to different problems, which means they call for different responses.
That is why emotional vocabulary matters more than most people think. Better labels do not just decorate experience after the fact, but rather help us understand in depth how we REALLY feel, what is causing it and how to act. They change what you notice while it is happening and what you do next. If you can tell the difference between fear and contempt, or boredom and loneliness, or admiration and envy, you stop treating unlike things as though they require the same move.
This matters most in relationships because a lot of conflict is really misclassification. "I am angry at you" might actually mean I am hurt that you did not notice me. Anger is so general, it means so many things to so many people. It might mean I feel small around you. It might mean I resent how much leverage you have in this situation. It might mean I am afraid and would rather strike first than admit it. People can spend hours arguing with the wrong label and never get near the actual issue.
It matters in self-command too. Different states need different responses. Loneliness is not handled the same way boredom is. Shame is not handled the same way fatigue is. Anxiety is not identical to dread, and admiration is not safely the same as envy. The person with a blunt inner vocabulary keeps reaching for one generic response and then wonders why nothing improves. Well, they themselves don't really know what needs to be improved.
That is also why a lot of public talk about emotional intelligence still sounds thinner than it thinks it does. It gives people a few big soft buckets and congratulates them for caring about feelings, but still doesn't give the tools to express those feelings accurately. Caring is not precision and you're not fixing anything without precision. A richer emotional vocabulary is closer to practical perception. It helps you see what kind of thing is happening before you act on it badly.
Learn your words. Not out of linguistic passion. Out of a desire for better mental health.