Journals can help the next generation to understand the past.
A Youtuber is currently renovating a chateau which was previously owned by a millionaire but never lived in until children during World War II needed a safe space to live for the duration of the conflict.
It is during that time of waiting that more than one occupant would write in a diary or journal, describing the building.
The building has since partially burned down. A Youtuber has purchased the estate and uses the diaries to understand what each room looked like and where every room might have been.
Often one believes that a diary or journal is mundane or not worth bothering. Actually, your journal might be of great importance to a future person who wants to understand the past.
View Dan’s discussion of a diary as he cleans out a chateau basement on his channel Escape to Rural France: https://youtu.be/cJwUNUJMnBU