'Don't forget about Humpty-Dumpty .... wear your FULL-FACE helmet every single time you get on the bike to do more then roll it into the garage.
I went down in the rain at about 20 mph and the back of my head hit the asphalt so hard I would have been a vegetable if not for my helmet.
Instead my biggest concern was the bent foot-peg and busted signal-lamp. (also had to replace the helmet)
EDIT: Also one of my daughters friends dad's was killed "just taking a ride around the block" right in his neighborhood when he slid on sand and hit his head on a curb at less then 10 MPH!
Helmet would have been hot and uncomfortable though!
I have no helmet.