> the reality of it is that you don't make much progress on any of them because as soon as one of them gets difficult, you just bounce over to another one that feels easier.
This really rang true to me. I have so many projects, and once I hit a significant technical wall, I usually start looking at other projects where I can get things done more easily and get gratification quicker. It really sucks, and Burkeman's recommendation of focusing on only one project at a time until you're done makes a lot of sense.
That said, it also requires a lot of determination to see something through. I think for me that is one of the most difficult things: having sufficient motivation to accomplish a task despite the difficulties. There has to be a great reward on the other side in order to push through the tough stuff. Only a few times in my life have I felt that sort of motivation for projects, and I'm not really sure what the throughline was between them, but I hope to capture that energy again someday.