Soulmates can still fight, he's seen it enough times when Odin and Frigga get into arguments, but that doesn't make the act of arguing easier. The connection between them pulls tight, like an emotional rubber band trying to pull two magnets of the same polarity together.

"You don't get to tell me how to feel! I know what this means, far better than you. I am trying to make it easier for you so we don't end up killing ourselves just to get away from each other, because for once in my life, I actually almost like living." The only reason he realizes he's shouting is because Thor and Captain Rogers come running out of the planning room they had set up.