Worst feeling in the world: Downshifting to keep a decent cadence into a 25mph headwind and the shifter goes "thud" because your already in the lowest gear. Cyclocomputer says 9mph and heart rate is 150ish.

Best feeling in the world: Upshifting to the highest gear because I'm bouncing out of the saddle with a 25mph tailwind. Cyclocomputer says 34mph and heart rate is 90ish.