I have found that making the bike commute decision the night before makes a big difference. I have my lunch (and extra snacks) ready in the fridge, most of the stuff I need in my panniers and bike cloths ready to go. I also have everything for my breakfast ready so all I have to do is cook it.

If I decide not to bike commute after all that, there's usually a pretty good reason. My commute is a challenging 18 miles (1 way) about half on gravel. It would be easy to just not feel like it, so the preparation and attitude the night before goes a long way.