This is especially significant if you’re a list maker.
To-Do List: All of the things you “must” do—commitments, duties, and tasks that must be completed—go into the Todo List. A single list, maybe divided into subcategories according on timeframe (today, this week, next week, next month).
Watch List: All the things in your life that you need to follow up on, wait for someone else to respond to, remind yourself of in the future, or otherwise recall go into the Watch List.
Later List: Everything else—everything you might want to do or will do when you have time or wish you could do—goes into the Later List.
If it doesn’t go on one of those three lists, it goes away.