Just change the channel~
When my kids were young, around 9 and 10, they used to bicker back and forth in the car. Not unusual by any means. But Zoe would really get wound up sometimes, and it was like watching and listening to a hysterical hyena!
Annoying would be putting it mildly!
One particularly aggravating car ride, Max looked over at me and said "Mom, let's just change the channel"!
We held invisible clickers in the air and went "click, click." Well, if that didn't work like magic. Max and I shifted to another channel. Zoe no longer had an audience. She actually started to laugh when she realized the significance of our action. Changing the channel became quite an effective way in our family to keep our cool, and the peace.
How simple when you think about it. When we find ourselves in a foul mood, or being pulled into someone else's foul mood, we can just change the channel. When you are starting to fall into one of your "fur lined ruts" (a behavior or pattern of thinking that is familiar but not helpful), change the channel!
It takes some practice, but it really works.