So I've developed my own method. I have found that I need to bring an exciting/challenging area up to the highest finish I can. That sort of sets the standard for the rest of the painting, and I have to bring everything else up to the same standard. It keeps me excited to work every day and makes it all seem like a fun challenge, and less like an impossible acreage to cover with my tiny brush.
I think every painter must have to develop their own way to approach a painting to stay engaged and motivated, and to avoid over thinking, or avoid just giving up out of frustration or intimidation. It's a psychological dilemma to solve every day in the studio.
I'd love to hear how you solve this. Or, if you are not a painter, how you keep yourself energized and excited for any challenging project? Do you do the fun parts first and crank out the boring bits at the end? Or do you save the best for last? Do you tackle the hardest things right away, or warm up with more manageable steps?