Having had good usage and some positive feedback on https://github.com/Aperocky/diaryman/blob/master/diaryman.sh, I decided to pack it into a pip package.
Essentially, all this does is to make creating diary super simple in the CLI, and resulting diary organized in a nice /diary/year/month/date.md hierarchy.
Having used this for a few years, I find this tool indispensable - I was never able to write diary consistently but once it was available via `diary` it became nature to utilize this to manage daily tasks at work and write personal reflections at home.