The Coworker Conundrum

I've been working at this company for about three years now and have gotten comfortable with most of my colleagues. There's this one person though, let's call them Alex, who I always find myself butting heads with on projects or during meetings. It started off as a misunderstanding where I thought they were intentionally trying to undermine me because their ideas seemed contrary to mine all the time. But then as we've worked together more and seen how everyone else interacts, it became clear that I was probably overreacting and just frustrated from stress. We've tried to have some candid conversations about it, which helped for a while. We both admitted our assumptions and agreed to check in with each other if things felt off. But as deadlines pile up and the pressure mounts, those good intentions tend to fall by the wayside again. Recently we were working on a big presentation and I made a comment about their approach that was more critical than it needed to be. It was pointed out by another colleague that my tone could have been perceived as harsher than intended. Now every time Alex sends an email or walks into the room, I feel this knot in my stomach. My knee-jerk reaction is still to think they're being unreasonable, but intellectually I know better and wonder if the problem lies more with me than them. We've both said that we value each other's contributions and want to collaborate effectively, yet it feels like progress has plateaued and now there are these awkward silences in meetings when our eyes meet. How do you move past this when you recognize your own part in creating a negative dynamic but also feel the other person doesn't take steps toward better communication or compromise? I really want to figure out how to make things better between us, but I don't know if it's just wishful thinking on my end. What should I do?