I hit a patch a few years ago on a ride along a MUP with a friend just as it was getting dark, went down and slid maybe 20 feet on ice (a thin layer of clear freezing snow melt running across the path). No damage other than a bruise on the side of one knee. While I was catching my breath after the fall, I suggested that riding in the road might be safer, he borrowed my road bike and left me his mountain bike to catch up to him on saying it was easier to handle. I was a bit paranoid of hitting ice again, but focusing on playing catch up solved that problem. I thought it funny at the time that he wouldn't ride in traffic to avoid ice and blamed my fall on poor bike handling.