Buy an old bike and change it into a singlespeed, one with gearing much lower than where you tend to mash. Ride it around the neighborhood (some place fairly flat where you don't/won't have to shift) and get use to spinning. Eventually spinning will become natural and you won't remmeber when you were a masher. You can do this with a geared bike as well, just set it in at the gear when you are spinning and don't shift.
BTW for those that "mash" you get no benefit from cycling which is intended as an aerobic sport. If you want to weight lift (which mashing is akin to) then go in a gym - its more efficient. Spinning is essential to cycling efficiently and keeping one heart healthy...
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Private docent led mountain bike rides through Limestone Canyon. Go to
letsgooutside.org and register today! Also available: hikes, equestrian rides and family events as well as trail maintenance and science study.