I think this is good advice if your goal is side income along with your high-paying tech job, or perhaps a lifestyle business where you earn enough passively to sit on a beach or ski more often than not. Personally that's where I am (the former) and most programmers who want to "make money online" probably are, too.
It's certainly not where the people who want to found a "startup" in the PG sense of the word, or be the CEO of a massive company, are. And (also paradoxically) I think most of them are probably in the same place the author is. Even if they have hobbies and passions, their #1 passion is probably "making more money."
1. Try and make 'the optimal thing'. Something easy to create, and so lucrative that I won't have to make anything else again
2. flail like the author describes
3. decide that no amount of money is worth feeling this way (or otherwise burnout via your method of choice)
4. make nothing for a while (~6 months for me)
5. start missing some aspects of what you used to do
6. gradually start making those things again, with the goal being to make those things.
Hopefully step 7 is profit, time will tell. If it's not, I'm ok with that too :)