Lots of books on the power of why being published these days. 
Lots of Gurus too making loads of money teaching on the subject.
I’m with the movement 100%.
I have seen a lot of Solopreneurs get beat up, give up and never see their dreams come true because of many things but a big reason is, they had a weak why.
Whatever your why is, make it deep, own it, let it keep you up at night and get you up at 4 am to work on your business/mission.
Many of us get caught up in the guru’s why. 100k sports car, big house, money, etc. Big problem, it’s not really our why thus tends not to drive or pull us hard enough to and across the finish line.
I believe if the why is big enough the details don’t matter. We will figure it out. We will hang in there. Will will succeed or die trying.
Once clear on your why writing it down at least once daily will help feed your fire. Why is because it stays fresh in our minds. Very useful to armer us against the shinny objects and other stuff tugging at our attention in the marketplace.
When we have a strong why, building a tribe and getting them to support your mission is much easier than without one.
The leader in the area of teaching the power of why is Simon Sinek right now.
Here is a video of his TED Talk
