Recently I have learnt a new one that helps somewhat, when I notice the grrrrr for the first time. First breathe a normal in breath, hold for a second or two, then continue to breathe in deeply, then a long slow breath out until all the air is gone and you are kind of yawning it out. And repeat. It is supposed to mimic our natural response to distress, like a child shudders their in breath when deeply upset. It's not a miracle cure for me but I find it helps somewhat.