Your mind is a powerful computer. But sometimes it works against you instead of with you. Your brain makes complex decisions and stores years' worth of information, yet there's one thing it doesn't do well: think of what you need when you need it, and forget about nagging thoughts when you don't need them.
When you're walking past the dairy section at the grocery store, you don't realize you've got only a day's worth of milk left in the fridge at home. When do you remember the milk? When you're standing in the kitchen with a box of cereal in your hand.
Short-term memory is a lot like RAM, the temporary memory on a personal computer. It's where you keep all the things you see and experience, and the thoughts that pop into your head throughout the day: "Gotta call the vet when I get home." "Didn't realize that new Italian place is there, should invite her out to dinner this weekend." "Wonder how much a Spanish class would cost." "Darn, I never emailed Jim back about those forms!"
Productivity expert David Allen says these types of thoughts all represent unfulfilled commitments you've made to yourself — what he calls "open loops" — that distract and overwhelm you, creating stress, anxiety, and a constant sense that there's too much to do: "Your conscious mind, like the computer screen, is a focusing tool, not a storage place. You can think about only two or three things at once. But the incomplete items are still being stored in the short-term-memory space. ...