Cycling keeps me in shape, and shaving off the extra love I've accumulated.
Being outside on the commute, against the wind, respiration getting heavier, passing by other riders/runners... passing the occasional car... sprinting to get the stop light on a countdown... setting new PRs on Strava... seeing the average MPH, total time travel, avg watts, etc improving steadily over time... the burn just mildly getting to the legs, arriving at school realizing even while the numbers have improved, you're not nearly as sweaty/winded as you were when you first began this journey. The new gear you attain over the months... learning new things about bikes, and generally just knowing that you're not part of the majority who are contributing daily to pollution... it all adds up to make that momentary struggle pushing 20mph on the commute all worth it, when nothing else matters, when there's no room to think about any of the other stresses in life, at home, worries about schedule conflicts and deadlines, etc.
Cycling keeps me sane. Commuting keeps me cycling.