The pencil marks on the doorframe measured more than height. They measured how long someone was paying attention.

What makes marks on a doorframe worth anything is not the heights. It is that somebody stopped what they were doing, found a pencil, and did it again a year later, and again, for a decade. Care mostly looks like that from the outside: an unremarkable action repeated long past the point where it was interesting. Anyone can do the first one, and almost nobody keeps going.

Start your own record of something and commit to the repetition. A photo in the same spot each birthday, a line written every New Year, a mark for a younger sibling. Its whole value comes from you still doing it in five years.