I don't ride to work everyday because sometimes I have to go other places during the workday or pickup the kids on my way home.
On the days that I can ride to work, I have to get over my morning mental fog and remind myself how much better I feel by the end of the day. My mental motivation problem is compounded with the knowledge of the long and steep hill that I have to tackle on my way to work. I just have to remind myself that the ride home is always a hoot and it only takes me half the time to get home as it does to get to work!
More than anything, though, is that I always feel much better on the days that I ride to work!!