Some lucky (or unlucky) people have hyperthymesia, a.k.a. Highly Superior Autobiographical Memory. These people can recall nearly every day of their lives in almost perfect detail. See a few individuals with hyperthymesia discuss their abilities.
People with hyperthymesia have an instant recollection of their memories no matter how far back. They don’t remember past events like a straightforward encyclopedia; rather, they remember things as they personally experienced the events. Good and bad memories and the emotions of the past are all still “fresh” in the mind. MRIs have been done on people with super memories, and it was discovered that a part of their brain, referred to as the nucleus, is dramatically larger. Regular people will never develop this “total memory” ability, but they can improve their memories by paying more attention to things that happen to them and mentally summarizing them at the end of the day.