As a parallel example of how tough cycling can be at times, I thought I'd share this comment from Captain Rudd walking across the Antarctic, which is exactly how I feel cycling into a fierce head wind at times:
“On one day I battled for eight or nine hours and covered two nautical miles. I thought ‘this is ridiculous’, stopped and put the tent up. I still had 800 miles to go. Eventually I made better progress and it was back on."
Specific board for this popular undertaking.