I have often read in self help websites that successful people maintain journals.
- What has maintaining journals to do with success?
- What should be written in a journal daily?
- How to maintain a daily journal?
I am talking about a personal journal, not a blog. Something to be read by you only, not the whole world.
And I am old school, I would do it by writing by hand on paper. You don't need digital copies. Of course it takes some time, but return on invested time is better than watching TV, IMHO. :-)
Since this is my most popular answer ever, it deserves bit of care and feeding: Why and how to write essay by Paul Graham, explaining the art of using writing to explore question to which you do not know the answer, and how this art was lost in our age of writing as part of argument to prove a point. Writing as exploring the possible problem area, trying different questions and looking where different answers will lead us.
Interesting book to read about such process is book by Antoine de Saint-Exupéry - Citadelle (titled in English: as The Wisdom of the Sands). Like his most famous book "Little Prince", it is about search of meaning of life. Unlike LP, it is for adult readers. In this unfinished posthumous book, you can see how writer tries different approaches to answer same question (what Paul Graham asks for), but because it is posthumous, Exupéry did not eliminated parallel approaches. Fascinating book to read about how mind of a writer (who writes about meaning of life) works.
Personally, I believe, life is repetitive. Things that you are experiencing now may be the same things you will experience in the future. By maintaining a journal you document how you react to a particular situation. In the future, you can re-read how you reacted and take heed.
For example, you make a business decision now and it goes kaput. In the future you are faced with the same situation. You can go back, re-read and analyze.
This puts you in a better position to make decisions.
Anything that you feel is important. Maybe you met somebody new. Write down what you observed about them - their dress, their body language, their way of speaking, their emotions, etc.
Went to an interview? Write down what you prepared. What you expected adn what actually happened. Was it a "good" interview? Was it "bad"? What made it "bad"? How can you improve?
I would prefer a well-written blog as it might help others, too. If you are not comfy with sharing the details online then you can maintain a Word document for each day or something like that.