In all seriousness, one of the trickiest things about writing as a line of work is the part that doesn’t look recognizably like work.
I’m currently in progress on a background project, and I’ve had to accept that as much as I would like to be charging ahead and putting words down on the page, doing that right now stands a high chance of producing material I’ll just have to cut later. I need to think.
The lack of a tangible sense of progress from thinking phases is totally a mental challenge of the writing process. I feel like learning how to do this, practically and mentally, has been part of my writing growth the last few years — not that I’ve totally gotten it figured out, but I find I need both active forms of making myself think about problems (free writing, excel sheet planning, brainstorming / mind-mapping, worksheeting) as well as just letting my brain have some stewing time. Reading books about writing is another adjacent thinking activity, because I can’t help but think about my book’s issues as I read craft advice. For a long time I thought I just needed to give myself the time, but months would pass without progress, so I’ve learned that I also need the active thinking processes to keep the problem top of mind and give me something new to chew on.