The day after Presidents' Day I pedaled in even though the day was starting out bad. My commute was more of the same with everyone seeming to drive half-awake and grumpy. None of the drivers did any thing absolutely stupid but there was more of not paying attention and not giving me much room. The ride home was only a little better. The next day was along the same trend. All-in-all the stress reduction from pedaling was nearly negated from people driving absent-minded and/or grumpy.
I normally only try to get 2-3 days a week in between Tuesday thru Thursday because Mondays and Fridays have a higher idiot factor.
Commuting for me is mostly to sneak in miles/exercise to something I have to do anyways. The environmental, cost savings, and stress reduction factors are just added bonuses.
With all of the environmental, traffic, and other hazards to deal with, what makes you say "f@#$-it I'm riding my bike today!"?