A list is useful because it removes the cognitive load of having to remember things. A list of things you might do is useful because you no longer have to keep them in mind, and hence you can think about more details. In some sense the size of the details in your list, relative to the overall project scope, indicates the subconcious ranking of their importance.
We keep a list of things that we would like to do, and what is currently preventing them from happening. Combine this with a list of things needing to be purchased and you have a fairly efficient way of ensuring steady progress. Keeping track of the progress of each projects also encourages completion, something that the 'visionary personality type' (or 'deluded crack pipe smoking slacker') has a tendency to not do.
Having said that, I do regularly feel that I have not made enough progress to justify my existence.