I focus so intently on the task at hand that stress, thoughts about problems, home, work, whatever have no maneuvering room in my head, and fall out of my ears along the road somewhere. It's why I feel so refreshed on arrival at my destination.
This. Always 100% focus, even on 4+ hour group rides while wheel sucking, which requires the highest priority focus.
Never been hit, but if it happens, I'm sure in my last seconds I will be thinking "OK, focus on your landing".