I can relate to so much of what you have described. I moved up through the ranks in my own industry until I was managing. It became a job that consumed my every waking moment.
I remember thinking that I could put the same energy into working for myself. I didn't resign, but rather stepped down to a position with minimal responsibility and then began the task of rearranging my time commitments to spend the majority of my life working for me, and the least amount of time working for others.
I've had to make some adjustments to my perception of what it is to be a 'success' and it is much harder for me to discipline myself without responsibility to others.
Freedom is a satisfying feeling, but somewhat daunting at times. It requires an immense amount of will and determination to make it happen.
Yes. If I'm to succeed, I'll have to put in the same hours of work into writing as I did with this job. Dicipline, that's going to be key