Reactivity is -- well, reactive: a physiological, fight or flight response, that can occur in seconds and result in lost tempers, emotional outbursts, or in worst cases emotional and/or physical abuse. (A good Wikipedia article on the fight or flight response: HERE. ) One of the most important tools for helping yourself and your partner in a rapidly escalating argument is to SLOW THINGS DOWN.
There are the tried and true ways: "Excuse me, I have to need to go to the bathroom", or counting to ten before you respond, but you know when you are in an argument, how you feel the urgency to respond and not let go!
So why not try something different. Put yourself in a timeout, after all it's what you do to the kids when they are having an emotional meltdown. And it is your kid part actually, that's out and driving the bus, isn't it? So time yourself out.
Make an agreement with your partner ahead of time, that the next time you get in a discussion that feels too intense, that you use the timer on your smartphone. You each get 45 seconds to talk -- no abusive language, no name calling, but 45 seconds to say your side. Then there is a 15 second silence, during which you breathe and meditate, relax -- this is not the time to be churning inside, formulating your next response, or going over how unfair your partner is, but rather a time of self-soothing.
After the 15 second silence, it is your partner's turn to talk. Then a 15 second silence, and your turn. Couples always report this works, until it doesn't -- when they have slowed things down and then stopped using the technique. So you have to stay in the process.
Slowing down and coming into the moment, into a conscious conversation with your partner, means you are going to have to deal with your own anxieties around intimacy, emotional engagement, and high emotions -- which is a good thing. It will allow you to see the real reasons you are arguing; then you can focus on solving the problem.