So how I manage productivity when I'm not always at 100% is to make sure I have multiple projects that require different amounts of mental effort. One of those projects is redrawing this naked person's hair in an easier manner for me that I figured out pages after this.

Everyone argues that you shouldn't go back and edit old work because that way leads to madness and you'll never make forward progression. Well, if I'm not mentally capable of forward progression but I can edit existing images then I'm going to do the work I can do. I won't sit on my hands doing nothing because peer pressure bluntly says no to the only thing I have capacity for.