I stopped fasted cardio in the morning the moment I fell on ice and bruised my leg and my knee was swallen. The temperatures were below 0 (I use the metric system, so let's say in the 20s F). and I was doing my morning prework half an hour cardio on the bike when I stepped on frozen cobbled street. I was sliding a few meters (feet, ok) and couldn't stop. The descent there is about 15% so it was difficult to stop. I felt pain, I felt terrible and helpless. When I tried to stand up on my feet, I couldn't move because it was too slippery even for walking. After that I took my bike and pushed it in the bushes. It was a horrible experience and after that I have ridden a stationary bike at the gym in the mornings. I still commute to the gym and then to work by bike but it's only 10 minutes ride and I don't freeze my a**. Sometimes in the afternoons or on the weekends I ride a bike when the temperatures are higher.