It's easy for a conversation to turn into a fight when you're distracted or multitasking. Body language and eye contact are a huge part of communication, and when you're not able to fully use them on the conversation at hand, it can often lead to a fight. Keep this from happening in your relationship with the "eye contact" rule: only have serious discussions when you're both able to make eye contact. Photo by Huskyherz.
My premarital counselor suggested this tactic after I told her my fiance and I bicker in the car a lot for some reason. She said that's actually pretty common among couples, because when you're driving, you're not (and you shouldn't be) fully engaged in a serious conversation. You're not facing the person, and more importantly, you're not making eye contact with the person. So it's easy to take things the wrong way and let them get out of hand. She suggested we adopt a rule to only have serious conversations when we're able to make eye contact -- so not while driving, doing something on the computer or phone, cooking, or whatever. Simply put, you want to make sure you're focused on the conversation.
Don't get me wrong, driving can also be a time for great conversations, too. Some of the best discussions I've had were on road trips. But the idea here is: when you're discussing a sensitive topic, it's easy to take things the wrong way; there's a sense of distance. You want to make sure you're fully engaged in the conversation so you can read each other well and empathise.