I really appreciate this comment - when I was working on my old startup, I felt exactly the same way.

I quit my old job and was working on what I wanted to, and yet felt this resistance that I couldn't explain. The nagging doubts that I was doing the right thing, that it wouldn't be good enough, and the fact that it would be all o n me if things didn't work out.

It's definitely one of those mental roadblocks that's hard to explain until you've been through it.