I use a single file, with standard headers, with a new entry for each day. I use `org-diary` to manage that:
https://github.com/skx/org-diary
Every morning I run `org-diary-new-entry` which inserts a new block. At the end of the day I commit this to a git repository and push it away for safety. I've got a work-log/journal going back a couple of years at this point.