A thing I like to do when travelling is to send myself a postcard from wherever I am. Some people find this a bit strange (analogous to how people also find it strange I go to the cinemas by myself, but that’s another story), but I really enjoy it.
Not only will I have a souvenir waiting for me when I get home, but it helps refresh my memory for years to come- what I was doing, how I was feeling, or just little details I noticed in places, such as the statues of Ave Maria at every street corner in Venice, or how Paris Métro is just a stinkbomb of pee waiting to happen. It’s a great and inexpensive way to keep track of the places you’ve been, as well as the little memorable experiences you’ve had along the way.
The tip is to find a nice postcard (something you’ll love to see when you return home) and start scribbling. You’ll thank me later 😉