Explaining Myself

I don't know why I can't do it. I just know that I can't.

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When I speak it sounds clear as day to me but to the opposing side, I sound "stupid, dumb annoying."
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How do I sound more clear? I read more that I can. I speak to people and ask for help. I feel like I am doing the right thing but it always comes out another way. My tone seems to make the situation worse. I lack confidence sometimes. The fact that I have no courage in my voice diminishes the point that I try to take across.
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When I was a little girl, I was afraid to stand up for myself in fear of the opposing side that had more anger in their voice from mine. It scared me. My Grandma was the only, and I mean the only one, who understood me. When It was time to have a sit down with Rissa, oh my, I would have a terribly hard time trying to communicate how I feel. But Grandma would come in and say exactly how I felt. Exactly. I never felt more understood. Now that I'm on my own I can never really understand myself. I still don't.
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Today I was helping a friend wrap saran wrap around my pack. We are heading back to the United States and our packs have to be secure. I'm holding the back pack and he starts giving me direction with a tone that I should already know what I should be doing. I ignore it. I'm frustrated. We are great together but when working with one another he says I lack the capacity to listen, to take direction. I am Stupid. Dumb. Bitch. I am too much in my feelings all the time.

I can't handle yelling, name calling, and points that I don't understand because my actions are just me. It's all me. my own self. I can't handle it. Am I being irrational?
How do I keep going?