I've just read a great blog entry comparing being a start-up entrepreneur to being an athlete in training for the Olympics. They've got it spot on!
http://www.cambrianhouse.com/blog/startups-entrepreneurship/olympians-an...

The author says that friends and family just don't understand why you work such long hours and put so much energy and passion into it. They don't understand why you are so tired so much of the time, and yet you keep going.

The problem is that they view it as work - while you view it as a calling. This is just something you have to do to be who you really are.

So here is why being an entrepreneur launching a start-up is like training for the Olympics according to this blogger:

* Both are all consuming
* Both span similar period of time (about 4 years)
* Bothe demand a lot of hard work, time, dedication and pain
* Both force you to make sacrifices
* Both are extremely addictive in their own unique way
* Participants in both are pursuing goals and glory - above and beyond money - for which they are willing to work extremely hard
* Chance of failure in both are high

But the author mentions that people find it much easier to understand someone putting in this level of work to compete in the Olympics, but just glaze over when it's about starting a business!