Before I put everything on my Mac, I used to hoard my datebooks, and even my old checkbooks so I could leaf through and think: Oh, in April of 1988, I bought a leather bag in the Village. I had dinner at Intermezzo in Chelsea. Ah, that's the date I called that guy I had a crush on and we went to the movies and he went right home afterwards. Alone.
There is something about holding those little pieces of history in your hand that bring it all back. No one really saves emails or texts, and if you do, it usually is for business, but it just isn't the same as having that paper or that card--that visual that's so much richer than an email catapulting you back to a specific time and place in your personal history. I used to laugh at my mother for saving everything I ever wrote, including my letters home from college. Now, I'm glad.
Details, in life and in novels, make all the difference.