Good question... I think I just knew there was something more exciting to ride than what I currently had. In Philly, I went from a kid's mountain bike (hitting my knees on the handlebars and shifters) to a beach cruiser to a raleigh 12 speed to my fixie in just over a year. I had worn through most of the parts on the 12 speed and wanted to build a bike, it made sense to me to try building a fixie. It's funny, I remember hating on fixed gear bikes...but then I tried one. I think that's the same story with most people. I just built a single speed for the hell of it recently, and it was the most uneventful ride I ever had... up the fixed gear!