Antarctica is the only place in the world where the temperature can reach 90 below zero. Mere existence in these conditions, let alone working, is challenging and difficult.
The same is true in the world of selling. To be a worldclass sales person or sales leader is challenging and difficult. Many valuable lessons for sales people can be learned from the famous race to the South Pole in 1911-1912, where temperatures reached 90 below zero and colder.