A different sort of record
Not every day has a milestone. A colour in the sky, a sentence someone said, or a particularly good lunch can be enough to make a small record of being there.
Make a line, not an essay
Keep the note short enough that starting is easy. One line beside a date is a practice you can return to without catching up on everything you missed.
Let there be gaps
A record with gaps still tells a story. It is yours, and it is allowed to look like a life rather than a streak.