Could you expand on it? What are the benefits, what have you gained by doing this?
Here's an example: the first time you learn a design pattern you can create a journal entry about that pattern with some psuedocode. Then next time you want to build something using that pattern, you can look at your journal. Even 10 years down the line and 3 companies later.
Does that help?
I've tried journaling before but I would rarely read it for anything. This is something I want try again.