Mentally? I think smile inside, you can still grip the mouth guard with a slight smile there, when you do it, your eyes smile too, your brain frees up slightly, it effects you in reverse but the same neuron path seems to fire up even though you dont actually have something to be smiling about just thinking smiling frees you slightly internally from the frustration.

Not the shaking of the head and laughing aloud trick to say Im not hurt,you are having no effect on me; thats a crock and you should be still moving on and wacking someone while they are doing that.