I can't write if I'm not in the right mood or if I'm not inspired.
Okay, yes, I can write boiler plate articles about index funds and how to make a budget(*), but I can't sit down day after day and grow a book consistently one hour at a time.
(*) This is what I mean by separating: Writing stuff I don't really care about.
The ERE book was written in spurts. Sometimes it would be a few weeks between writing anything. Some days I'd spend 12+ hours writing. Other days 5 minutes.
So my habits are those of an amateur, not a professional, even if the writing holds up to professional standards.