The cool weather and lower humidity take more out of me on Fall rides. I just slow down, ride the gravel roads, enjoy the fall foliage, and don't worry about miles. No drop in enthusiasm, but big drop in miles. These slow Fall rides on almost car free gravel roads are fun, and shorter rides leave more time for Fall chores, of which there is no shortage. Hang in there, and don't let arbitrary goals rob you of the joy of cycling.