You might think Entrepreneur and Endurance are synonyms and it can certainly appear that way from the outside.  But there is a very specific zone where endurance is truly defined and tested in building a business.  It is called the "Valley of Death".  The Valley of Death is the period of time when a product is launched and you are working to commercialize it and find acceptance in the market.   That is the hardest part of building a business and where many companies need their greatest support structures.  Everything coalesces in the Valley of Death (marketing, product, sales, operations, talent, regulation, finance, etc.) because we're vulnerable in the Valley.  We are public with our product.  There will be so many signals tempting you to turn back, to run as fast as you can to the safety of the pre-launch process, retool, and try again.  Endurance challenges that instinct.  Endurance drives you forward, giving conviction an edge over self doubt.  Endurance can be trained and tested, as it is in many areas of life.