I ride all winter on a 14 mile commute. Commuting is a great motivator, especially to answer that perennial question, "You didn't ride your bike today, did you?."

To better define the challenges of winter (= cold) riding, I would offer this definition of a cold ride, from the Winter Cycling Forum: One on which your water bottle freezes solid---a function of temperature and distance (time). For my 14 mile one-way ride, it happens at about 15* F and below.