My father has always been obsessed with the history of his parents who fled Vietnam to settle down in a French immigration camp for many years, to the point where he has developed an expertise in the niche of the French/Vietnamese decolonization. Obsessed, because it always felt odd to me to see him stuck in the past like this - by writing and speaking about it.
Now I started writing myself, I wonder: aren't we all stuck in the past in some way? The present is an accumulation of past experiences. If we want to have an impact on our present - and thus, on our future - we must acknowledge the past to overcome it.
Document the past to build the present. It's not just a strategy to deliver content, or as Gary Vaynerchuk from VaynerMedia puts it: "Document, don't create". It's a way of life.
If you write about the present, you're not doing anything. You can only write about the past, the future, or an alternative dimension from your imagination.
If you write about the future, you live a deferred life. It's a form of escapism. Thinking too far ahead is dangerous because it builds up cognitive barriers preventing you from acting now. Don't set goals, develop habits instead. Tell your plans wisely. You don't want a to-do list or a past decision to dictate your life. Living in the future is locking your present.
On the other hand, writing about the past is building upon it. Acknowledge it, accept it, outgrow it. Tell others what's been done, how, and why. Journaling in public is incredibly productive because humans learn by experiencing new things, by interacting with each other. Writing things down makes you go through the whole process.