Most days do not announce themselves. They arrive, get used, and leave without leaving anything behind — and a year later you can name maybe nine of them.
This is the argument against that.
Write it the same night.
Memory edits. It rounds the sharp bits off within a day and rewrites the rest to suit whatever mood you are in on Thursday.
Count the boring things.
Hours slept, money gone, whether you left the room. None of it feels worth recording until you have two years of it in a line.
Do not perform.
Nobody else is reading. An honest bad day is worth more than a flattering paragraph, and it is the only kind you learn anything from.
The unexamined life is not worth living. The over-examined one is exhausting. Aim somewhere between.