I forgot my helmet the other day on a nighttime run to the grocery store. I made it about a half mile before realizing that something was missing...and then determining what it was. I've been wearing a helmet since 2008, and it just didn't feel right.
I ended up going back home to get my helmet. I felt vulnerable, especially since my town is not known for attentive drivers or enforcing DUI laws. But the wind in my hair felt nice for that short mile.