...there's less confusion when you die. Also, fewer hurt feelings when Cousin Tater gets the antique urinal, because you clearly specified it went to him and not Cousin Rufuss (who would have claimed it should go to him, but now he'll just have to make do with your great-grandfather's best bedpan instead).
Today is La Dia de Los Muertos, the Day of the Dead, and several cultures look on it as a day to honor their ancestors. Some folks have a picnic on the family cemetery plot, decorate the tombstone, tell stories, drink (and pour onto the grave) a few libations.
What a fine day to acknowledge that you will one day be under that sod rather than over, and try to make life easier for the people left beind to sort out your mess (it's always a mess when it's someone else's stuff you're sorting through, even though you loved them deeply and miss them keenly)?
If you don't have one, go get one. Look for forms online, in your local office supply store, or at your friendly family lawyer's office. Fill it out, get it witnessed and notarized, and head over to the courthouse to file it so it's on record. You'll save the people you love some real heartache, later.
If you have got one, good for you!! Now go make those revisions you've been meaning to make for the last decade but keep putting of or forgetting about.
If you don't, the court will take care of it when you're gone - and isn't that a cheerful thought??