The current havoc and distress being caused by he who shall remain nameless, takes a toll on most of us. My sister has always had a bit of road rage, but it's gotten worse than normal lately. Believe me I have my moments too.
The thing that has helped me, deal with the anger, frustration, and anxiety, are things I have learned through a combination of life experiences, good advice, and a lot of therapy. I most often go into distract mode. When I feel the more distressing emotions start to kick up, I give myself a short window of time to acknowledge it, curse a blue streak in private about whomever, or whatever is causing it, then I go do something like play an internet game, or listen to an audio book or music, while doing household chores.
If I am with others, when it happens, I start paying attention more to my surroundings, like looking at the trees, and the sky, or smelling the scent of food coming from a kitchen. It doesn't make whatever upset me go away completely, but it allows my emotions to settle down enough, so they don't overwhelm me completely. In therapy they called it Dialectical Behavior Therapy. The therapists told me it's about the science of the brain, and training it to switch which side of the brain is in control. It hasn't helped me 100 percent, but I'd say it works about 70 percent of the time.
Also I have started to try and find some positive things even when things go wrong. Like last night I was happy that my sister, and I were in sync about leaving the concert early, and going through the drive through. We often disagree with each other, so it was a nice change. Also I thought I get to go home, take my dog out, and go to bed earlier than I planned. Those things all lifted my mood.
Hope this helps some. Hope you're blood pressure check goes well.