People rely a lot on their memory, which is wildly fallible, but that doesn't mean people can absorb an 18-to-do list. It is much better to concentrate on a few things. Very usa phone list criticism, and the way we have to translate it is, most of the time things boil down to three. Now there may not be enough research to show that three is some kind of hard limit, like the average number of digits we can retain, but the Count limit of three makes a lot of sense.