Ever hit a parked car?
I did, one time, way back when I was a teenager.
It was nighttime. The street was pitch black. My bike didn't have a light. I was very pissed-off about something - I don't remember what now. I was cruising along in the right lane, just spacing off gazing down at the front tire when WHAM. I came to an immediate stop and my face must have left a dent on the trunk hood. I think I broke my glasses but there was no permenent damage. I don't ride like that any more.
Also, my brother's little boy came screaming into the house one day with his face covered with blood. He had been riding his bike with his eyes closed and his face hit a mirror on a parked truck. He's OK now too.
Don't try either one of these things at home.