I'm able to post this today because I wore a helmet when cycling along the Union Canal one month ago. Over handlebars at speed directly onto the top right of my head, didn't even have time to let go of the handlebars. Four stitches above my right eye and lots of bruising but my skull would have been fractured without the helmet.
Just thinking about how hard my helmet encased head hit the ground sends shivers down my spine.
I sometimes took my helmet off when on that canal but for some reason that day I didn't.