The more words you own, the less you have to rely on volume to make a point.

Shouting is what happens when the right word is missing. Name the exact thing that bothered you and you need no force behind it, because the sentence does the work on its own; without that word, pressure is all you have left. People reach for loudness out of frustration with their own vocabulary at least as often as out of anger. More words means more ways to be understood first time.

Hunt for the specific word as soon as you feel your voice rising: dismissed, rushed, left out, overlooked. Say that one instead. Collect a few by reading, and notice how much less you repeat yourself.