I have self-doubt, obviously.
We all do to some degree because we wouldn't have survived childhood otherwise.
It was a good thing our self-doubt kicked in before we decided to climb that rotted tree, or rusted fence, or crossed the street without looking both ways.
But overall our self-doubt was built for a bygone era when lions, and tigers, and bears were a more rampant threat and therefore it wasn't safe to keep your guard down for too long.
To excel in the modern world I think you need an abundance of self-confidence and the evidence is clear - Donald Trump, Hillary Clinton, George W. Bush, Mark Cuban, Steve Jobs, etc...
These people accrued massive amounts of wealth and power and they're definitely not self-doubters.
They make decisions and then move onto the next decision.
Some could argue their over-confidence leads to serious vulnerabilities, but it's hard to detach their level of success from their level of confidence.
1) Set goals. Pursue those goals - furiously. And then only if you're way behind expectations should you sit down and consciously work out a new strategy with pen and paper in hand (not by replaying your problems in your head over and over).
2) Success leaves tracks. Follow those tracks. Breakdown with pen and paper someone or something you admire. Figure out how him/her/it became successful and then apply those lessons to yourself or your business.
3) Entrepreneurship Tip: Minimize your risk as much as possible. I try to spend very little because I'm living off of my savings. I moved to Bangkok for its affordability. This will give me a greater buffer to work on Live to Challenge before I need to make it profitable.