I keep a journal, mainly to give my fountain pens something to do.
I really only have two rules with it. Write something every day, and once a page is started, it needs to be filled by the end of that day. Doesn't matter how many pages are filled in a single day, but every page started is filled.
As for what, it's whatever. If I have nothing to write, but I have the urge to put pen to paper, I will often write down that I have nothing to write. A good gripe about having nothing to say can take care of a paragraph or two.
When I started the journal, a good bit of it was nothing more than a running commentary about the pens and inks I was trying out that time. If nothing else, it gave me handwriting practice.
Hopes, fears, and dreams? Not here. This is writing for the sake of writing. Sometimes something profound comes out. Other times it's complaining about how the dehumidifier is baking me or why I can't mow the lawn today. More often the latter.