How does Elon Musk pull off being the chief executive of both Tesla Motors and SpaceX, chairman of SolarCity, philanthropist through his Musk Foundation, which recently provided aid to the Gulf Region, and father to five boys? He works twice as hard as the average guy.

If other people are putting in 40 hours in a week, and you're putting in 100, you will achieve in four months, what it takes them a year to achieve. That's the type of work ethic an entrepreneur needs to have, according to Elon, in this segment, called "Lesson Learned."

This is the final interview in my four-part interview series with the founder and CEO of Tesla Motors and SpaceX. Watch the short interview to hear his lessons.