How do I start my business when I don’t believe that I will persevere?

I have had a long-term successful career working in software. I enjoy my job a lot and don’t want to leave full-time employment, at least not right now. However, I believe I have something more to give to the world based on my experience and knowledge in my field. I imagine writing a book with the ideas and techniques I’ve developed. I can envision building a consulting practice around such a book. But the idea of doing that is daunting. I think, “I should start with something more manageable, like a free downloadable booklet with the same ideas.” Then I could build up a readership, and a mailing list. I could even sell related downloadable booklets while writing the book I have in mind, and by the time I got the book published (or published it myself) I would have already started building up an audience, and a potential client base for consulting.

I have had grand ideas like this in the past, and didn’t make much of them. Yes I had a book published one time… but I didn’t feel proud of it, and didn’t promote it. I did at one time have a pretty good readership for my online writing but again, I failed to capitalize on it.

I don’t believe in my ability to make this happen. I’m too much of a dilettante, too unwilling to take on discomfort, too old, too used to being an employee and not an entrepreneur.

I also have thoughts like, “I don’t want to leave my high paying technology job but otherwise I don’t have time to write anything, not a book and not a booklet, maybe not even a blog post.”

And yet I feel so underutilized in the world and like I have so much more to give.

I can see that my thoughts are psyching me out and preventing me from taking action. Can you suggest a next step for me? Decide on a 30-day plan and use the approaches in “how to get it done”? Set an impossible goal of writing the whole book in six months? Give up entirely–spend my days eating fat bombs, drinking wine, and reading ask-a-coach Q&As?