Writing things down like this helps you to think about more that one problem at once.
It's difficult to keep more than one problem in your head, but writing them down means that you can forget about something for a while and think about new things.
That means that when and if you come back to reading the old things that you wrote about, you can start again from the same place. But of course your brain may have been working on the old things while you weren't watching it, so sometimes there are ready-made new thoughts that come to mind as soon as you read the old posts.
So it makes you more able to think about more things, and it makes you better at it.