I'm in my early thirties, and I'd say only in the last 5 years or so have my thoughts on life been relevant. My diaries from prior are much more simple minded, so not so beneficial for me, but the more recent stuff is. Or, I guess seeing growth always is beneficial. Yes, I do think getting the thoughts on paper/screen is very important. Has a way of clarifying those thoughts so that they are more permanent.
Steemit is an interactive diary for me. I like it when I hear of people using it in the way you are. It's more than a ploy for income.
I found something I wrote when I was in my early 20's, 47 now.
It was also more simplistic, certainly idealistic.
Funny I wrote that I wanted to be able to do the splits as a goal...still working on that one lol..
Anything that is improving is great, helps to build realistic confidence based on competences. Which I guess is much better than complaining about the world and projecting anger and tension....I have tested that and it really sux lol..
Have a great day :)