THIS. Producing a webcomic has taught me two big lessons regarding productivity: 1. Finding the right 'amount' of preparation, and 2. Embracing 'good enough'.
When I was gearing up to start drawing pages, I spent probably 6-9 months writing the script, making character reference sheets, and figuring out the basic layout/map/structure of important places. I had a list of things I wanted to design before I started drawing. I got through about 80% of that list before I felt like I was stalling-- I had the immediate, and most important, stuff designed, and everything else was either side characters or wouldn't come up for more than a year, and then only briefly.
I was... mostly ready. So I recognized the stalling, squashed it, and started.
And now that I've begun... I've learned the art and zen of 'Good Enough'. I need this to be sustainable long term, after all. I produce a page a week (that I add to my buffer-- I'm not posting each page as I make it, eek!), and I need that to not burn me out. So I do as good a job as I comfortably can, and embrace that while I COULD make it better, I'll never be able to make it perfect, and trying to do 'absolutely the best that I can for every page' will absolutely be unsustainable.
So each page that goes out is 'good enough', because done is better than perfect. And tbh, my skills have been improving anyway, even without trying my absolute hardest on each page, because I'm drawing a page every week.
This whole webcomics thing is so cool, you guys. It's so cool.