One year ago today I decided to start a log of my bike rides. I can't remember why, but after years of "just riding" I sat down and created a little spreadsheet, and have since made one row entries for each ride; the route, the miles, and the time (if known). This is pretty cool, because now I know that in the past year I did 210 rides, for a total of 6,608 miles, an average of 31 miles per ride, or 127 miles per week. Wow, that is so cool!
I believe this is an excellent example of the metric magic. For me, measuring works. Your mileage may vary :)