I’ve written fairly consistently for about 15 years now. If doing it digitally, I recommend Obsidian. One reason being that the files are plain text so regardless of what app you use you’re not locked into some obscure format. Another reason is that the wiki-like format makes it easy to make summaries of each day, each month, and each year. So it’s really easy to go back and find when big events happened.

I’m in the process of copy/pasting old entries (obscure formats) and it’s been cool to see what I was thinking way back when. I went through some dramatic moments during my dating years and so it’s nice to see how much better life is now as a married dude.

The only negatives I can think of are: (1) how private are my thoughts if digital, and (2) do I ruminated about bad things if I’m writing about complaints and/or hopes for the future too much?

That being said, you can encrypt the folder with something like VeraCrypt and sometimes you have to force yourself to count your blessings instead of complain.