Why checklists work
One of the things I've been doing much more over the past couple of years is using checklists, the virtues of which I've written about before. Recently I have been thinking about why they work, and came to the obvious realization: they're a form of talking to the duck.
Before you write down a checklist, you may think that you understand everything that you need to do, but it is in your head and your head is very good at fooling you. Like explaining something out loud, writing it down shines a bright light on all of your assumptions and fuzzy thoughts and forces you to clarify them, or at least exposes them to you.
(With a checklist specifically, one of the things it shines a light on is our belief that we can keep track of more things than we actually can, which is one of the important roots of fragile complexity. Usually writing a detailed checklist shows me not only that I was fuzzy on some steps but that I was leaving some out entirely.)
Checklists have auxiliary purposes too, of course; for example, they are communication with co-workers, they are confidence boosters, and they reduce the amount of things that you have to think about so that you can focus on paying attention to the work you are doing right now. And crossing completed items off is a useful reward.