So many good responses, but this one is a treasure by CACycling (and seemingly part of many responses so far) - It rang a bell with me as I sit in my office most days and look over at the beautiful bike leaning against the window. The ride home gives me plenty of time to unwind and is an exuse to not get home right away (needed to stop at the library, pub for a pint, or just take a different route)
While I have many days I don't feel like getting up a half hour early to ride, I've yet to have a day when I get to work and wish I hadn't ridden.