I usually skip cyclecommuting when I'm sick or there's snow on the roads. There might be a third case if I'm banged up from a fall. I just fell today and got some nice road rash on my left leg. Also a few scrapes on my right arm. But if I feel as good as I do today, then I'll most likely be riding into work tomorrow. Every time I take the train, I'm reminded of why I cyclecommute. Things like train schedule, subway jam packed, and delays are all avoided with the bike.