Started this ride on fire and then ran into a doozy of a climb up to 10,200 feet. From 9,500 to 10,200 there was a lot of walking the bike which would be the theme of this event. On the second day, I felt great, but had to really pace myself with the entire day between 8,100 and 10,800 feet. Near the end of the day, I was stuck walking for almost two straight hours. Just could not turn my pedals on any type of upward slope. As I was walking, a pickup truck rolled up next to me and offered a ride. In a moment of supreme weakness, I accepted the ride. My 1200K effort was officially over. For the third day, I sat around Walden. Ate several large meals and rested with a book in hand enjoying the views of the mountains (spectacular). I rallied on the fourth day and set off before dawn with the rest of the riders. Lots of smiles on this day and it felt great to get back down to reasonably thick air at 5,000 feet. Looking forward to returning to Colorado to retry this event. Lessons were learned. Hard efforts two miles above sea level required a mental adjustment and physical acclimation period. Now it's time to pivot and apply my mental energy to recovering and prepping for the next adventure on the calendar.