 Left to its own devices, it will naturally gravitate toward things you don't want to dwell on. Have you ever had to work hard to remind yourself of something dumb you said a long time ago? Do you need a to-do list to overthink an embarrassing situation for the 8th grade, even though you're now in your 30s? Did you need a note on your calendar to make sure you'd spend the whole weekend thinking about why your boss called a meeting with you on Monday morning?