One of my first trips was NYC to Niagara Falls. My knees hurt so bad in the finger lakes region, I would pedal with one leg and then push down on the other leg with my hand. I lost all hope of riding across the country.
After that trip I rested, and regeared my bike to have a much lower climbing gear. When I flew to Seattle and started up the Cascades a few days later, I couldn't believe how much easier those big mountains were than the two miles straight uphill back east.